on Just Publishing Advice:
A memoir and autobiography are similar genres that detail a life story.
In literary circles, the definition between the two is sometimes a little fuzzy.
Both record the life story of the author and are written in the first-person point of view. That is, I was born, I lived, and I married the man/woman of my dreams.
Perhaps the only way to define each genre is to say that one is a factual biography. The other is a memory of a certain time.