The concept of Dashavatar (Ten Avatars) has tremendous significance even in today’s jet age. Evil has been present at all stages in the evolution of mankind and the Dashavatar in a way brings out this evolution through the triumph of good over evil.
The most famous of the divine incarnations of Lord Vishnu are Rama, whose life is depicted in the Ramayana, and Krishna, whose life is depicted in the Mahabharata and the Bhagavad Gita.
The four great era or epochs in Hinduism are: Satya Yug, Treta Yug, Dwapar Yug and Kali Yug. Satya Yug or the Age of Truth is said to last for four thousand divine years, Treta Yug for three thousand, Dwapara Yug for two thousand and Kali Yug will last for one thousand divine years. It is also believed that three of these great ages have already passed, and we are now living in the fourth one. The four ages are said to symbolize the four phases of human evolution during which man gradually lost the awareness of his inner self. Another theory explains these epochs of time on the basis of the degree of loss of righteousness in the world. It says, during Satya Yug only truth prevailed (Sanskrit Satya = truth), Treta lost ¼ truth, Dwapar lost ½ truth and Kali is left with only ¼ truth. Evil and dishonesty has replaced truth in the last three ages or yugs.