An autobiography is a history or account of a person's life written by that same person, or, as is typical, written with a professional writer.  A memoir, on the other hand, may appear less structured than a formal autobiographical work. Memoirs are often about part of a life, and frequently a public part of a life, rather than the person's whole life from youth to old age. They can also relate to a specific event or period written using personal knowledge or specialised sources.