An extra section at the end of a book has which name?

An epilogue is a section of writing at the end of a book that takes place outside of the setting, perspective, or frame of the story. It often intends to provide closure and resolution by explaining what happens after the main narrative arc has ended. As it is in the main body of the text, the epilogue is still part of the story. It shouldn't replace the novel's ending but merely provide a grace note for the story to close on.

Source: Reedsy