An archive is a collection of older things — documents, books, movies, or something else — that's meant to preserve them. Archives tell us about history.
An archive involves old stuff — specifically, a collection of old stuff, often put together by a librarian. Newspaper archives collect old newspapers, usually all copies of a paper from a certain date onward. There are movie and music archives. Most museums have many types of archives within them. And it's always a good idea to keep an archive of important files on your computer. When you put something in an archive, you're archiving it.