There are now many people claiming to be an "Avatar," claiming to be Divine incarnations on Earth, and they deck themselves with jewels and gold and want to be worshipped and followed. The real meaning is "messenger," someone who delivers a message on behalf of God.
A genuine avatar is not vain or proud, making proclamations about themselves.
Vishnu is just a symbol of an aspect of the Divine that reaches out in order to help humanity.
It is stated in one of the Hindu scriptures, through the mouth of Krishna, that he comes into the world any time religion declines and degenerates.
Yet we find a central theme throughout all Hinduism that describes the supreme manifestation of the Divine.
Of course, over the centuries, the character of Krishna has been understood by people at many different levels, some accurate, some inaccurate.
Vishnu is just one of the many symbolic representations of God in the Hindu pantheon.