Ryan Singer from 37signals on the term UX (User Experience) :

It means too many things to too many different people. Instead I focus on individual skills. Once you understand the individual skills, you can assemble them into a composite system without blurring them together. For software design, the core skill among all user-facing concerns is user interface design.

The term UX should be used only by people that run the whole gamut of tools and techniques; words are cheap. Looking at the see also list , there’s even more to cover, out of the top of my head: accessibility and usability testing.

But a good UI should take the front line.

But for software makers, I recommend starting with a strong understanding of UI by itself. The fundamentals can take you very far.