A Unique Value Proposition is meant to explain to investors and employees the value that a business is offering to its customers. A value proposition is the promise of value to be delivered, communicated, and acknowledged. This helps everyone to understand the primary focus of the business and the needs of the customers.
Typically, the UVP is used by management and explains how this offer is different from competing value offerings and why the customer would choose you over others.
(This practice is under development and is part of the book Startup, Scaleup, Screwup.)