The qualification of a Being as an Avatar varies by the God. Some Gods prefer to leave the term to their own blood, others call the most faithful ones on a planet an Avatar. At the end of the day, the term Avatar covers loyal and trustworthy participants of religious traditions and practices. The lists of active Avatars are large, the ones about the dead ones even larger, but the background numbers blow all statistics apart.
It is seen that Avatars often resemble their Deity close and in great detail. These similarities are not of physical nature, but more the fact that these Avatars often act and react like their more powerful creator.