Usability is sometimes contrasted with user experience, and although usability certainly overlaps with user experience, they are not quite the same thing. Usability is a part of the big picture that is overall user experience.
Thomas Baekdal has written a great article where he highlights the difference between the two:
Usability is about the “ability to use” something. The aim for a usable product is to make it easy to use.
A product has a high level of usability when:
* It requires less mental effort to use
* the frequency of mistakes using it is less, or when the mistakes are less disastrous
* it is more powerful, where “more powerful” means that it can be used to do more or do it faster
* it is more learnable, that is, when a person can figure it out quicker
User-experience is not like usability – it is about feelings. The aim here is to create happiness. You want people to feel happy before, during and after they have used your product. To do that you need to take all kinds of things into consideration. Things like:
* Colors moods
* Audio feedback
* Visual feedback
* Show-off effect
* Emotional effect
This is much much much harder to achieve. None of these things can be accurately analyzed. It is a touchy feeling kind of thing.
Why, for instance, does a Audi S6 give you a much better user-experience than a Ford Focus? I mean, in terms of usability they are pretty much the same.
He also gives some great real world examples
Jared Spool in his post The Difference Between Usability and User Experience explains the difference by giving an exampe of a guy shopping for digital camera online.