footnote vs. endnote

an explanatory or documenting note or comment at the bottom of a page, referring to a specific part of the text on the page.

a minor or tangential comment or event added or subordinated to a main statement or more important event.

to add a footnote or footnotes to (a text, statement, etc.); annotate:

a note, as of explanation, emendation, or the like, added at the end of an article, chapter, etc.