Language preservation strives to prevent languages from becoming unknown. This can happen when a language is no longer taught to younger generations, and the elderly people who do speak the language fluently die.
Language is an important part of any society, because it enables to people communicate and express themselves. When a language dies out, future generations lose a vital part of the culture that is necessary to completely understand it. This makes language a vulnerable aspect of cultural heritage, and it becomes especially important to preserve it. According to the United Nations Educational, Scientific, and Cultural Organization (UNESCO), from facts published in their "Atlas of Languages in Danger of Disappearing," there are an estimated 6,000 languages spoken worldwide today, and half of the world’s population speaks only eight of them.  More than 3,000 of the remaining 5,992 languages are reportedly now spoken by fewer than 10,000 people. Ethnologue, a reference work published by SIL International has cataloged the world’s known living languages, and it estimates that 417 languages are on the verge of extinction. 
There are different factors that can put a language in danger of becoming extinct. One is when a language is no longer being taught to the children of the community, or at least to a large number of the children. In these cases, the remaining fluent speakers of the language are generally the older members of the community, and when they pass on, the language dies out with them.
Child speakers are not enough to ensure the survival of a language however. If the children who do speak the language are relocated to another area where it is not spoken, it becomes endangered. Political and military turmoil can also endanger a language.  When people are forced from their homes into new lands, they may have to learn the language of the new area to adapt, and they end up losing their language. Likewise, when a country or territory is successfully invaded, the population may be forced to learn the invader's language.
A language can also become associated with a lower social class.  In this instance, parents will encourage their children to use the language used more often in society to distance themselves from the perceived lower class. Within one or two generations of this occurrence, the language can easily be lost.
When a language dies, the knowledge of and ability to understand the culture who spoke it is threatened. As each language dies, science in linguistics, anthropology, prehistory and psychology are threatened.
There are different ideas about the best ways to preserve a language. One way is to encourage younger generations to speak the language as they grow, so they will then teach their children the language as well. In many cases, this option is nearly impossible. There are often many factors that endanger a language, and it is impossible to control each of these factors to ensure its survival.
The Internet can be used to raise awareness about the issues of language extinction and language preservation. It can be used to translate, catalog, store, and provide information and access to languages. New technologies such as podcasts can be used to preserve the spoken versions of languages, and written documents can preserve information about the native literature and linguistics of languages.
Computer scientists estimate that a mere 10% of the world's languages are used online. Google allows its users to select from 36 languages, and 28 of those are European in origin, which clearly marginalizes Native and Indigenous languages. The International Internet provider VeriSign estimates that 65-70% of all Internet content in is English. 
Using written documents to preserve information about the native literature and linguistics is also not without potential problems. Just because a language is written down, this does not mean it will survive. Written information in book or manuscript form is subject to acid issues, binding problems, environmental monitoring problems, and security concerns.
Technology can also be used to preserve the integrity of spoken versions of languages. Many of the same techniques used in recording oral history can be used to preserve spoken languages. Preservationists can use reel-to-reel audio tape recordings, along with video recordings, and new technologies like podcasts to record spoken accounts of languages. Technology is also vulnerable to new technology. If the ability to listen to or watch audio tape recordings or video tapes is lost, then the language was not preserved.
The Administration for Native Americans has published the "Reference Guide for Establishing Archives and Repositories," which explains why language repositories are vital to long-term language preservation efforts.  The guide offers practical advice on what to preserve and why, it explains what a language repository is, how to build one, the costs involved, and other resources about creating an archive and repository.