In the Trinity of Gods of the Hindu pantheon, Vishnu is the Protector and Maintainer. He is said to be the physical manifestation of spiritual consciousness. In Rig Veda, he is referred to as Vamana, younger brother of Indra, who helps Indra in regaining his kingdom. Later, the Brahmanas mention Lord Vishnu as the Supreme God, whereas, in Vishnu smriti and Bhagavata Purana he is referred to as one of the Gods of Hindu pantheon.
Incarnations of Vishnu:
Through the three great ages or yuga cycle that we have passed (such as Satya, Treta, Dwapar yuga) to arrive into our present Kali yuga, Vishnu incarnated on Earth many times in human and animal forms to save the world. It is said that as the Preserver of this World, Vishnu has incarnated amongst humans whenever balance of good and evil has been toppled or order replaced by disorder and anarchy. According to the Puranas, Vishnu had incarnated ten times as different avatars.
Different avatars of Vishnu:
Vishnu arrived in the form of a fish in Satya yuga to rescue Manu and the seven great sages (sapta rishis) from the Great Deluge (when a great flood threatened to submerge the Universe). He gave directions to Manu and saved the Vedas from being destroyed.
During the Churning of Milky Ocean, Mount Mandara was used by Devas and Asuras to churn the Ocean, but impact on the ocean was so much that Mount Mandara began to sink. At this point of time, Vishnu took the form of a turtle (kurma) to support the Mount and prevent it from sinking. As it is popularly known, Mount Mandara represent human mind in the ocean of Universal Consciousness.
Once during Satya yug, the demon king Hiranyakasapu had stolen the Goddess Bhudevi (who represents the Earth). To rescue Her from grip of the demon, Vishnu took the form of Varaha or boar. A long drawn fight ensued between the demon and Vishnu or Varaha. Finally, Varaha was able to recue Earth or Bhudevi from the demon.
Once during Satya yuga, the demon king Hiranyakasapu received a powerful boon from Lord Brahma: that he cannot be killed by man, animal, inside or outside his palace, during day or the night, on earth or star or with any weapon. After being blessed with this boon, the demon became a terror for the Gods and saints and began to perpetrate torture to all. To save the holy souls, Vishnu appeared with body of a man, and head and claws of a lion, and tore off the demon with his claws on his thighs at the threshold of the demon’s house and courtyard.
Once, the demon king Mahabali (grandson of Prahlad) had grown so powerful and arrogant that the Gods had begun to fear him. They sought help of Vishnu who disguised himself as a short Brahmin (Vamana) and requested Mahabali for a gift of three feet of land which the king gracefully granted to him. The Vamana grew to the size of a giant, kept one foot on land and one on the sky – the demon king realized that it was Vishnu, so he bowed his head and Vamana kept his foot on his head. This granted immortality to the king but he promised to recede to his kingdom in hell.
Parashuram was the sixth Vishnu Avatar who appeared in the Treta yuga to avenge the Kshatriyas for their arrogance and unrighteousness. He was gifted with an axe by Shiva, who also taught him martial arts.
Rama was the seventh avatar of Vishnu who was the son of king Dasaratha of Ayodhya. He was an example of a righteous man and a pious king. He renounced his kingdom to his brother Bharata and lived in the forests with his wife and brother Lakshman. When his wife was stolen away by demon king Ravana, he fought against him and rescued her.
Krishna, the eighth avatar of Vishnu had a brother Balarama, who is also considered to be a Vishnu avatar sometimes. Krishna is known for his philosophy and spiritual views as the modern avatar. He plays a prominent role in Mahabharata in which he relates his principles of life and sense of duty chronicled in Bhagavat Gita. His words are the tenets of karma yoga in Hinduism. Due to Him the good principles and purpose of life finally triumphed in the great battle. With disappearance of Krishna Dwapara yuga came to an end and Kali yuga began.
Gautama Buddha was the name given to Siddhartha Gautama, after he became “the enlightened one”. He renounced a princely life to become an ascetic and become awakened and discover reasons for pain and suffering in human society and eradicate them.
Puranas reveal that Kalki, the last Avatar of Lord Vishnu will descend on a white horse at the end of Kali yuga. He will wipe out unhealthy and immoral practices to help human society on the track of righteousness.