Matza (also Matzah, Matzoh, or Matsah, Hebrew: מַצָּה, in Ashkenazi matzo or matzoh, and, in Yiddish, matze) is a cracker-like unleavened bread made of white plain flour and water. The dough is pricked in several places and not allowed to rise before or during baking, thereby producing a hard, flat bread. It is similar in preparation to the Southwest Asian lavash and the Indian chapati.
Matza is the substitute for bread during the Jewish holiday of Passover, when eating chametz—bread and leavened products—is not allowed. Eating matza on the night of the seder is considered a positive mitzvah, i.e., a commandment. In the context of the Passover seder meal, certain restrictions additional to the chametz prohibitions are to be met for the matza to be considered "mitzva matza", that is, matza that meets the requirements of the positive commandment to eat matza at the seder.
There are numerous explanations behind the meaning of matza. One is historical: Passover is a commemoration of the exodus from Egypt. The biblical narrative relates that the Israelites left Egypt in such haste, they could not wait for their bread dough to rise. The resulting product was matza. (Exodus 12:39). The other reason for eating matza is symbolic: On the one hand, matza symbolizes redemption and freedom, but it is also (lechem oni), "poor man's bread." Thus it serves as a reminder to be humble, and to not forget what life was like in servitude. Also, leaven symbolizes corruption and pride as leaven "puffs up". Eating the "bread of affliction" is both a lesson in humility and an act that enhances one's appreciation of freedom.
Another explanation is that matza has been used to replace the pesach, or the traditional Passover offering that was made before the destruction of the Temple. During the Seder the third time the matza is eaten it is preceded with the Sefardic rite, “zekher l’korban pesach hane’ekhal al hasova.” This means, “Remembrance of the Passover offering, eaten while full.” This last piece of the matza eaten is called afikoman and many explain it as a symbol of salvation in the future.
Bread was often a symbol of salvation in ancient Israel. This is related to the idea that the Garden of Eden was fertile with bread trees. The benediction over bread was, “motsi lechem min ha’arets,” meaning, “brings forth bread from the earth.” This implies “that in the future He will bring forth bread from the earth,” or the paradise of the Garden of Eden will be restored. After the Temple cult, sometime in the first century, the saving symbolism of bread was applied to matza. Matza became a substitute for the pesach because bread was already a symbol of salvation in the Jewish community.
The Passover Seder meal is full of symbols of salvation, including the opening of the door for Elijah and the closing line, “Next year in Jerusalem,” but the use of matza is the oldest symbol of salvation in the Seder. 
At the Passover seder, it is customary to eat matza made of flour and water only. Matza containing eggs, wine, or fruit juice in addition to water is not acceptable as it is considered to become leaven. Matza made with these items without the use of water is acceptable during the remaining days of the holiday, although most strictly Orthodox Ashkenazi Jews will not eat this kind of matza at all during Passover.
There are five grains that may not be used during Passover in any form except for matzoh.
Wheat and spelt (biblical spelt is now more correctly identified as emmer wheat) are both in the genus Triticum and anything else in the genus is likewise forbidden. Oat-grain is practically gluten-free and belongs to a different tribe than wheat, spelt, rye and barley. Millet and teff are borderline; it takes a few days for them to rise. Concerning Identification of שיבולת שועל "oats" see מיני דגן (Clarification: In modern Hebrew כסמת is used for Buckwheat, which is not a grain at all.)
Matza dough is quickly mixed and rolled out without an autolyse step such as might be used in leavened breads. Most forms are docked with a fork or a similar tool to keep the finished product from puffing in the same manner as a tortilla or pita bread, and the resulting flat piece of dough is cooked at high heat until it develops dark spots, then set aside to cool (and, if sufficiently thin, to harden to crispness). Dough made from the five grains is considered to begin the leavening process 18 minutes from the time it gets wet, and sooner if eggs, fruit juice, or milk is added to the dough. In reality, though, the entire process of making a matzoh takes only a few minutes in efficient, well-organized modern matzo bakeries.
After baking, matza may be ground into fine crumbs, known as matza meal. Matza meal is used to make matza balls and is added to other foods, such as gefilte fish, to hold the ingredients together instead of flour. Kosher for Passover cakes and cookies are made with matza meal, which gives them a denser texture than ordinary baked goods made with flour. Coarse matzo meal is known as matzo farfel.
There are two major forms of matza, with several subcategories. In the United States, the most common form is the hard form of matza which is cracker-like in both appearance and taste, which is used in all Ashkenazic and most Sephardic communities. Many Mizrahi, Yemenite Jews, Ethiopian Jews, Hispanic and Latin Sephardi Jews traditionally made a form of soft matza. In those communities, matzo looks similar to pita while in others it can resemble a tortilla. However, it is made under proper supervision, just like the hard form of matzah. The soft form of matza is only made by hand, and generally with shmurah flour, as described below, like traditional "Shmurah Matza".
Among Ashkenazi matza, one can distinguish between what is called shmura matza — a round matza about a foot in diameter — which is made by hand, and machine-made matza, which is usually square and much smaller. Shmura ("guarded") matzo (Hebrew מַצָּה שְׁמוּרָה maṣṣā šəmūrā) is made from grain that has been under special supervision from the time it was harvested to ensure that no fermentation has occurred. In addition, it is made with the intention of using it to fulfill the commandment of eating matza on the first night of Passover.
(The same shmura wheat may be formed into either handmade or machine-made matza, while non-shmura wheat is only fashioned into machine-made matza. Moreover, although it is possible to bake shmura-style matza from non-shmurah flour, such matza is rarely produced today, although before the invention of machine-made matza it was quite common.)
Besides their shape, handmade and machine-made matza taste distinctively different. Handmade matzo is dense and chewy, while machine-made matza is lighter and crispy. Shmurah matza is generally available only around Passover and is more expensive.
Various commercial brands of matza come in flavored varieties, such as poppyseed- or onion-flavored. For those who cannot eat wheat, it is possible to buy oat and spelt matza with kosher certification. Organic wheat matza is also available. Chocolate-covered matza is a favorite among children, although some consider it "enriched matza" and will not eat it during the Passover holiday (Chocolate-covered matza should not be confused with "chocolate matza," a flat confection of chocolate and nuts that resembles real matza).
Many Haredi or ultra-orthodox Jews are extremely scrupulous about the supervision of their Matzah, as eating leavened products during Passover is liable to the biblical punishment of Kareth, thus many have the custom of baking their own Matzo, or at least participating in some stage of the baking process. Ultra-Orthodox Shmurah Matzah is typically expensive, generally between $10–$20 per pound, but sometimes costing up to $50 per pound for special varieties with particular stringencies.
Among many Hasidic Jews, only hand made shmurah matzah may be used, in accord with the opinion of Rabbi Chaim Halberstam of Sanz, who ruled that machine-made matzoth were chametz. According to that opinion, hand-made non-shmurah matzoth may be used on the eighth day of Passover outside of the Holy Land. However, today such matzoth are generally not made.
However the non-Hasidic Haredi community of Jerusalem follows the custom that machine-made matzoth may be used, with preference to the use of shmurah flour, in accordance with the ruling of Rabbi Yoseph Chaim Sonnenfeld, who actually ruled that machine-made matzoth may be preferable to hand made in some cases.
Matzot are used not only by themselves but in several roles in Passover cuisine where they can substitute for flour or pasta. In English-speaking countries, where Ashkenazic culture dominates, matzo balls and matzo farfel are widely used in soups and as pasta, as well as matzo meal being used in baked goods such as cakes. Matzah brei is another popular dish of Ashkenazi Jewish origins made from matzo fried with eggs.
A sort of pancake, called a matzo meal pancake, made from matzo meal (powder ground matzah) egg and milk and fried is also eaten as a substitute to normal pancakes.
Egg Matzah are matzot that are usually made with fruit juice, often grape or apple juice instead of water. Not all egg matza is made with actual eggs. There is a custom among some Ashkenazic Jews not to eat them during Passover, except for the elderly, infirm, or children, who cannot digest plain matzo, although they are considered to be kosher for Passover if prepared otherwise properly.
The issue whether egg matzah is allowed for Passover comes down to if there is a difference between the various possible liquids that make flour wet. Water facilitates fermentation of grain flour, but the question is if fruit juice, eggs, honey, oil or milk also do it. The Talmud (Pesachim 35a.) states that liquid food extracts do not cause flour to leaven the way that water does. For this reason flour mixed with other liquids would not need to be treated with the same care as flour mixed with water according to this view. However, other Talmudic commentaries (Tosafot) say that such liquids only produce a leavening reaction within flour if they themselves have had water added to them and otherwise the dough they produce is completely permissible for consumption during Passover, whether or not made according to the laws applying to matzot. As a result, Rabbi Yosef Karo, author of the Code of Jewish Law, (Orach Chaim 462:4.) granted blanket permission for the use of egg matzah (or any other matzah made from non-water-based dough) on Passover. Many egg matzah boxes no longer include the message, “Ashkenazi custom is that egg matzah is only allowed for children, eldery and the infirm during Passover.” In any event even amongst Ashkenazi Jews it is permissible to retain Enriched Matza in the home during Passover, it just may not be consumed.
Another view of this is that since the Hebrew term for egg matzo is matzo ashirah (Hebrew: מצה עשירה), literally, "enriched matzah" or "rich matzah", Egg matzo cannot be used to fulfill the requirement of eating matzo at the Passover Seder. This is because such matzo would be considered "rich", while the matzo eaten at the Seder is called "poor man's bread" (Hebrew: Hebrew: לחם עוני) (Deut. 16:3)
A basic principle of whether a given dough can be used for mitzva matzo is that doughs that do not have the potential of becoming chametz by simply sitting for 18 minutes cannot be made into mitzva matzo. Thus, a dough made from juice, etc., is of doubtful validity as mitzva matzo and may be used for the mitzva only in cases of illness or age.
Those who contend that Ashkenazi Jews should not eat egg matzah cite Rema (Orach Chaim ibid., 4) ruling that the custom among the Ashkenazim is to refrain from using Egg Matzah on Passover at all, unless it is necessary for children or the elderly who would have difficulty eating regular Matzah. Commenting on Rabbi Yosef Karo's permission to use egg matzah, the Rema responded "…in our communities, we do not knead (matzah) dough with fruit juice.…And one should not change from this unless in a time of emergency for the sake of a sick or old person who needs this" Those who follow this prohibition of eating egg matzah on Passover also include chocolate covered matzah, grape flavoured matzah and the many other varieties available.
Commercial matzo is often available during the year, both in flavored and plain forms. It is used in cooking (e.g. matzo ball soup made from matzo meal) or eaten as a snack. During the year, Ashkenazim treat matzo as bread, requiring washing before and full Birkat Hamazon afterwords. Sephardim normally treat it as a cracker and accord it the special status of bread only during Passover. Because of a tradition in some Ashkenazim circles that says that passover matzo should not be eaten during the year, some matzo not made for passover is intentionally made in a way that invalidates it, such as using malt in the product. These matzos bear the message, "not kosher for passover."
According to Western Christian belief, matzo was the bread used by Jesus in the Last Supper as there he was celebrating Passover; Communion wafers used by Roman Catholics for the Eucharist are flat (Orthodox Christians use leavened bread, as in the east there is the tradition that leavened bread was on the table of the Last Supper). In Koine Greek matza became known as ἄζυμος, Greek for unleavened bread. The term is no longer widely used in English but was used by the Catholic Church in the Douay-Rheims Bible.