means A short, memorable phrase used to sum up a brand, product, or piece of media in a catchy way.

from A compound of 'tag' and 'line.' 'Tag' traces back to a word for a hanging bit or label, the kind of small dangling thing you attach to something larger — and a tagline is just that, a little verbal label clipped onto a brand. The theatrical world used 'tag line' for the closing line of a scene or speech that punched home the point, and the advertising and entertainment sense grew from that idea of a final, clinching line, becoming common in 20th-century American usage.