The Experience in UX design
One of the most common misconceptions people have is that User Experience Design is all about usability. It’s easy to see why – usability means that a product is both usable and useful.
The empty room is usable, but it’s not useful until you fill it. It all depends on what furniture you choose and where you put it.
In software, “the room” a user enters is never empty. Every software product has a user-facing side that was built for people to interact with. That interaction becomes an experience they go through when they use the product. It’s the UX designer’s job to make that experience a great one.
The primary goal of any good designer is communicating the intended message, the one that leads to a positive user experience.
A practical guide for creating UX documents: Communicating the User Experience (pdf)