Beliefs and practices
Within Hinduism a large number of personalities, or 'forms', are worshipped as murtis. These beings are either aspects of the supreme Brahman, avatars of the supreme being, or significantly powerful entities known as devas. The exact nature of belief in regards to each deity varies between differing Hindu denominations and philosophies. Often these beings are depicted in humanoid, or partially-humanoid forms, complete with a set of unique and complex iconography in each case. In total, there are 33 million of these supernatural beings in various Hindu traditions.
The origin of the name Shiva means "the supreme one". Adi Sankara, in his interpretation of the name Shiva, the 27th and 600th name of Vishnu sahasranama, interprets Shiva to mean either "The Pure One", "the One who is not affected by three Gunas of Prakrti, Sattva, Rajas, and Tamas" or "the One who purifies everyone by the very utterance of His name." Swami Chinmayananda, in his translation of Vishnu sahasranama, further elaborates on that verse: Shiva means "the One who is eternally pure" or "the One who can never have any contamination of the imperfection of Rajas and Tamas".
Through these transcendent categories, Śiva, the ultimate reality, becomes the efficient and material cause of all that exists.
Many denominations of Hinduism, such as Vaishnavism and Saivism, teach that occasionally, God comes to Earth as a human being to help humans in their struggle toward enlightenment and salvation (moksha). Such an incarnation of God is called an avatar, or avatāra. In some respects, the Hindu concept of avatar is similar to the belief found in Christianity that God came to the earth incarnated in the form of Jesus. However, whereas most Christians believe that God has assumed a human body only once for a specific purpose, Hinduism teaches that there have been multiple avatars throughout history and that there will be more. Thus Lord Krishna, who is not only viewed as an incarnation but also source of all incarnations, says:
Whenever righteousness declines (Yada yada hi dharmasya, glanir bhavati bharata)
And unrighteousness increases, (Abhyuth-thanam adharmasya)
I incarnate myself as a human; (Tadat-manam srijamyaham)
I come into being from age to age (Sambhawami yugay yugay) 
The most famous of the divine incarnations are Rama, whose life is depicted in the Ramayana, and Krishna, whose life is depicted in the Mahābhārata and the Bhagavata Purana. The Bhagavad Gita, which contains the spiritual teachings of Krishna, is one of the most widely-read scriptures in Hinduism.
There is also a "hidden avatar" mentioned in 11th canto of the Bhagavata Purana.
Some consider Balarama, brother of Krishna to be the ninth avatar of Vishnu, and delete Buddha. The Buddha avatar, which occurs in different versions in various Puranas, may represent an attempt by orthodox Brahminism to slander the Buddhists by identifying them with the demons. Helmuth von Glasenapp attributed these developments to a Hindu desire to absorb Buddhism in a peaceful manner, both to win Buddhists to Vaishnavism and also to account for the fact that such a significant heresy could exist in India.
The pantheon in Śrauta consists of many deities. Gods are called devas (or devatās) and goddesses are called devis. The various devas and devis are personifications of different aspects of one and the same God. For instance, when a Hindu thinks of Ishvara as the giver of knowledge and learning, that aspect of Ishvara is personified as the deity Saraswati. In the same manner, the deity Lakshmi personifies Ishvara as the giver of wealth and prosperity. This does not imply that Ishvara is a kind of supreme god or lord of all the other deities; Ishvara is just the name used to refer to God in general, when no particular deity is being referred to. Devas represent certain forces. For instance, Agni has one aspect as the flame, but this flame symbolises the psychological power associated with Agni—namely, the power of will. Agni can be called God-will. Similarly Indra is the God-mind; Sarasvati is the power of inspiration, not merely of learning.
The devas constitute an integral part of the colorful Hindu culture. These various forms of God are depicted in innumerable paintings, statues, murals, and scriptural stories that can be found in temples, homes, businesses, and other places. In Hinduism, the scriptures recommend that for the satisfaction of a particular material desire a person may worship a particular deity. For example, shopkeepers frequently keep a statue or picture of the devi Lakshmi in their shops for financial prosperity. The elephant-headed deva known as Ganesha is worshiped before commencing any important undertaking, as he represents God's aspect as the remover of obstacles. Students and scholars may propitiate Saraswati, the devi of learning, before taking an exam or giving a lecture.
The most ancient Vedic devas included Indra, Agni, Soma, Varuna, Mitra, Savitri, Rudra, Prajapati, Vishnu, Aryaman, and the ashvins. Important devis were Sarasvati, Ushas, and Prithvi. Later scriptures called the Puranas recount traditional stories about each individual deity, such as Ganesha and Hanuman, and avatars such as Rama and Krishna.
Shiva and Vishnu are not regarded as ordinary devas but as Mahādevas ("great gods" ) because of their central positions in worship and scriptures. These two along with Brahma are considered the Trimurti—the three aspects of the universal supreme God. These three aspects symbolize the entire circle of samsara in Hinduism: Brahma as creator, Vishnu as preserver or protector, and Shiva as destroyer or judge.
The main devas are (vide 6th anuvaka of Chamakam):
The main devis are:
In their personal religious practices, Hindus may worship primarily one or another of these deities, known as their "Ishta Devata," or chosen deity. The particular form of God worshiped as one's chosen ideal is a matter of individual preference, although regional and family traditions can play a large part in influencing this choice. Hindus may also take guidance about this choice from scriptures.
Although Hindus do worship deities other than their chosen deity from time to time, depending on the occasion and their personal inclinations, it is not expected that they will worship, or even know about, every form of God. Hindus generally choose one concept of God (popular choices include Krishna, Rama, Shiva, or Kali), and cultivate devotion to that chosen form, while at the same time respecting the chosen ideals of other people.
Hinduism is a very rich and complex religion. Each of its four denominations shares rituals, beliefs, traditions and personal gods with one another, but each sect has a unique philosophy on how to achieve life's ultimate goal (moksa, liberation). For example a person can be a devotee to Shiva and a Vishnu devotee but one can practice the Advaita Vedanta philosophy which believes there is no difference between Brahman and a person's individual soul. Conversely, a Hindu may follow the Dvaita philosophy which stresses that Brahman and the soul are not the same. But each denomination fundamentally believes in different methods of self-realization and in different aspects of the one supreme God. However, each denomination respects and accepts all others, and conflict of any kind is rare.
Vaishnavism, Saivism, and Shaktism, respectively believe in a monotheistic ideal of Lord Vishnu (often as Lord Krishna), Lord Shiva, or Devi; this view does not exclude other personal gods, as they are understood to be aspects of the chosen ideal. For instance, to many devotees of Krishna, Shiva is seen as having sprung from Krishna's creative force. Ganesha worshippers would connect themselves with Shiva as Shiva is the father of Ganesha, making him a Shaiv deity. Often, the monad Brahman is seen as the one source, with all other gods emanating from there. Thus, with all Hindus, there is a strong belief in all paths being true religions that lead to one God or source, whatever one chooses to call the ultimate truth. As the Vedas - the most important Hindu scriptures state: "Truth is one; the wise call it by various names" (transliterated from Sanskrit: Ekam Sat Viprah Bahuda Vadanti.)
Smartism, is monist as well as a monotheist and understands different deities as representing various aspects and principles of one supreme entity, Brahman or parabrahman. Teachers such as Swami Vivekananda, who brought Hinduism to the West, held beliefs like those found in Smartism, although he usually referred to his religion as Vedanta. Other denominations of Hinduism do not strictly hold this belief.
A Smartist would have no problem worshiping Shiva or Vishnu together as he views the different aspects of God as leading to the same One God. It is the Smarta view that dominates the view of Hinduism in the West. By contrast, a Vaishnavite considers Vishnu as the one true God, worthy of worship and other forms as subordinate. See for example, an illustration of the Vaishnavite view of Vishnu as the one true God. Accordingly, many Vaishnavites, for example, believe that only Vishnu can grant moksha.. Similarly, many Shaivites also hold similar beliefs for Shiva.
There are some Hindus who consider the various deities not as forms of the one Ishvara, but as independently existing entities, and may thus be properly considered polytheists.
Although the panentheistic tendency in Hinduism allowed only a subordinate rank to the old polytheistic gods, they continued to occupy an important place in the affections of individual Hindus and were still represented as exercising considerable influence on the destinies of man. The most prominent of them were regarded as the appointed "loka palas", or guardians of the world; and as such they were made to preside over the four cardinal and (according to some authorities) the intermediate points of the compass.
Thus Indra, the chief of the devas, was regarded as the regent of the east; Agni, the fire, was in the same way associated with the southeast; Yama, lord of death and justice with the south; Surya, the sun, with the southwest; Varuna, originally the representative of the all-embracing heaven (atmosphere), now the god of the ocean, with the west; Vayu (or Pavana), the wind, with the northwest; Kubera, the god of wealth, with the north; and Soma with the northeast. In some traditions, Ishana—an aspect of Shiva—is regarded as the regent of the northeast and Nirrti the regent of the southwest.
In the institutes of Manu the loka palas are represented as standing in close relation to the ruling king, who is said to be composed of particles of these his tutelary deities. The retinue of Indra consists chiefly of the Devas, gandharvas, a class of genii, considered in the epics as the celestial musicians; and apsaras, lovely nymphs, who are frequently employed by the gods to make the pious devotee desist from carrying his austere practices to an extent that might render him dangerous to their power. Narada, an ancient sage (probably a personification of the cloud, the water-giver), is considered as the messenger between the gods and men, and as having sprung from the forehead of Brahma. The interesting office of the god of love is held by Kamadeva, also called Ananga, the bodyless, because, as the scriptures relate, having once tried by the power of his mischievous arrow to make Siva fall in love with Parvati, whilst he was engaged in devotional practices, the urchin was reduced to ashes by a glance of the angry god. Two other divine figures of some importance are considered as sons of Siva and Parvati, viz. Karttikeya or Skanda, the leader of the heavenly armies, who was supposed to have been fostered by the six Knittikas or Pleiades; and Ganesha (lord of troops), the elephant-headed god of wisdom, and at the same time the leader of the dii minorum gentium.
Goddesses are worshiped when God is thought of as the Universal Mother. Particular forms of the Universal Mother include Lakshmi, Sarasvati, Parvati, Durga, and Kali. Shaktism recognizes Shakti as the supreme goddess. The concept of Mahadevi as the supreme goddess emerged in historical religious literature as a term to define the powerful and influential nature of female deities in India. Throughout history, goddesses have been portrayed as the mother of the universe, through whose powers the universe is created and destroyed. The gradual changes in belief through time shape the concept of Mahadevi and express how the different Goddesses, though very different in personality, all carry the power of the universe on their shoulders. Jagaddhatri and Mariamman are other significant female deities.