Memoirs focus on a particular, very significant time in an author’s life. It’s not like an autobiography, where you write down all the important points of your life from beginning to present day as a series of facts. A memoir writer talks about one point in their past like a story, hoping to help or inspire people based on what they’ve learned.
Memoir = memory
Memories are an important part of that storytelling, and are used by a writer to focus on important moments and the feelings they bring.
Here’s an example.