Origin story
Vishnu is the preserver of the cosmos, the deity who sustains dharma whenever it declines. He reclines on the serpent Ananta in the milky ocean and returns to the world in avatar after avatar, from the fish Matsya and the dwarf Vamana to Rama and Krishna.
Vaishnavism holds Vishnu to be the supreme being, known also as Narayana and Hari. His conch, discus, mace and lotus mark sound, mind, strength and purity, while the serpent Ananta stands for infinity. In Kerala the tradition is anchored at temples such as Padmanabhaswamy, Guruvayur and Thirunavaya, where the deity is worshipped in his many forms.
Source: Wikipedia: Vishnu — https://en.wikipedia.org/wiki/Vishnu