Unique Selling Proposition

In advertising, at first, but now also in marketing, a USP is a short and snappy “sales message” intended to stick in the memory. It’s predicated on the unproven theory that people can only remember one thing (ie. from an advertisement). Thus a USP is supposed to hold some claim or logic, making it a sales message as opposed to a slogan.

A USP differs from UVP (Unique Value Proposition) in that (a) it refers to a piece of creative messaging work, not a positioning concept, and as such (b) it’s short and memorable. 

USP is also a theory of advertising, branding, etc. And it’s currently the most popular such theory. But like all other theories of messaging, marketing, branding, PR, and advertising, it is unproven and probably unprovable.