Also known as あとがき (atogaki) in Japanese. A literary device typically found at the end of a work.

The contents of the afterword tend to be from the author's perspective, giving insights on how the ideas for a work were formed, or how the work itself was created. Sometimes, someone other than the author may use the afterword to give commentary on the work's context (e.g. history or culture surrounding the setting).
あとがき 後書き