In publishing, a masthead is a list at the top of a page that includes the names of editors, writers, and owners, as well as the title of the newspaper or magazine. You'll usually find the masthead on one of the first few pages.
In the UK, a masthead is slightly different: it's the title page, also known in the US as the "nameplate." American publications include editorial and ownership information on the masthead, while their British counterparts call this the "imprint." The sense of a masthead as the "top of a newspaper or magazine" comes from the word's original meaning, "top of a ship," from mast, "long pole that holds a ship's sail."