The word avatar means fallen. The Infinite fallen from its supreme state into an apparent state of finitude and sorrow is avatar. The entire universe is an expression of the infinite reality, but an avatar is ever conscious of his own infinite nature.
The Supreme, on account of his unquestioned freedom, by his own perfectly free will, takes upon himself the matter envelopments and manifests himself in a particular embodiment in the world, for serving the deluded generation of the time. To the Lord, this “ignorance” is a pose assumed, not a fact lived.
In the avatars, we watch a greater effulgence of the divine consciousness constantly expressed, and they embody forth whenever there is an excessive decline of dharma, righteousness and the rise of adharma, unrighteousness in the world.
Though the Lord is unborn and changeless in his nature, and ever a Lord of matter, yet, keeping his maya, power of delusion perfectly under his own control, he comes into the world through his own free will, fully conscious of his own divine status and unchallenged prerogative.