Vishnu is known as "The Preserver/ Protector" of the universe within the Trimurti, the holy trinity that includes Brahma("The creator") & Shiva("The destroyer")
Whenever the world is threatened with evil & destructive forces, Vishnu descends in the form of an avatar (incarnation) to restore the cosmic order and protect Dharma.
Dashavatar are the ten primary avatars of Vishnu out of which, Rama & Krishna avatars are the prominent ones.

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Yash Deval
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