re: Avtar in Hinduism?
Brahman is different to Brahmin and brahma. According to my knowledge Brahman is seen as the highest reality which surrounds all and cannot be defined. It is in a way similar to a formless God. In Sanskrit it is defined as sat chit anand meaning truth consciousness bliss.this is the subjective experience one feels as they get closer to this reality. It is in a way like a universal spirit. This concept exists in Buddhism and Jainism also.
Calypso probably knows more about it.