How are memoir and autobiography different from each other?

A 'narrative' refers to any piece of writing - usually a story - which 'narrates' - your typical, chronological tale. Many slave autobiographies are titled 'narratives' as they are the story of a life.

An autobiography doesn't have to be entitled 'narrative' - nor does the demarcation 'narrative' mean the story is autobiographical.

Some slave 'narratives' are not autobiographical - they are fictional. However, as they are telling a story, they are still 'a narrative'.