USP means different things to different people. To some it means Unique Selling Proposition and tho others it means Unique Selling Position.
"Even while you creatively imitate others, remember that it's also important to be different. Distinguish your business or practice from all the rest. Make your enterprise special in the eyes of your customer or client. That is the goal I want you to pursue. How do you get your business differentiated? By creating a Unique Selling Proposition - or USP". (Read More on the Unique Selling Proposition by Jay Abraham).
A Unique Selling Proposition is a statement that identifies what makes a person, product or organization different from competitors.
Note: A Unique Selling Proposition is not the same as a Unique Selling Position
A Unique Selling Position is more about the posture and position your sales staff will take in regards to your target market. Generally this is more than just your proposition, but includes your company philosophy and story as the unique principle. The Unique Selling Position is sometimes considered your "Why". Simon Sinek does the best job of describing the "why-driven" position of a truly great company.