What makes a biography a biography?

A biography documents someone's life. It differs from other reports about people in that it covers a whole life or a substantial part of a life. An account of an actor's role in a film is far from a biography but a book that describes his life after finding fame can be, even if it ignores events before fame.

A biography can deal with specific aspects of a life such as relationships with other people or just professional activities. Others can be an account of the person, friends, family, work, feelings, leisure activities and more.

An auto-biography is also a biography but written about oneself.