avatara (Sanskrit: avataranam) means "the decent of Supreme Being on earth for the ascent of man"), means ‘descent’, and usually implies a deliberate descent of the Divine into the mortal realms to reveal the Absolute Truth to humanity and remind them of their true divine nature.
Avatara concept is used primarily in Hinduism for descents of Vishnu whom Vaishnava Hindus worship as the Supreme God. Shiva and Ganesha are also described as descending in the form of avatars. The Ganesha Purana and the Mudgala Purana offers the details of Ganesha`s avatars specifically, the avatars of Vishnu also carry a greater theological prominence than those of Shiva or Ganesha and upon examination relevant passages are directly derivative of the Vaishnava avatara lists.
The most traditional form of Avatar within Hinduism is the incarnations of Vishnu, the preserver or sustainer aspect of God within the Trimurti or Hindu Trinity. Dasavatara is the ten Avatars of Vishnu in the Garuda Purana. Matsya is first avatar of Vishnu. However, the ten most famous descents of Vishnu are collectively known as the "Dasavatara" and denote avatars who were most prominent in terms of their influence on human society.
The first four of the avataras appeared in the Satya Yuga and the first of the four Yugas or ages in the time cycle were described within Hinduism. The next three avatars appeared in the Treta Yuga, the eighth descent in the Dwapara Yuga and the ninth in the Kali Yuga. The tenth is destined to appear at the end of the Kali Yuga after some 427,000 years.
Though Avatars may appear in different forms at different times, places and circumstances, yet they are all the manifestations of the One Supreme Lord.