If I may... I'm not sure the original question was accurately answered, that being "What is an Avatar"... (granted, the balance of the question does have to do with "activating an Avatar).
An Avatar is the use of anything in place of the original. On source describes it in this manner: "...In computing, an avatar is the graphical representation of the user or the user's alter ego or character..."
Another source indicates: "...An avatar is something that embodies something else.
In Hinduism, for example, the different gods could take many different forms, and when they took human forms, the human was their avatar..."