Chris Bank does a great job of tackling UX and UI in this post.

When designing a website, you want your UX to be as positive as possible — you want your users to enjoy being on your website, that’s kind of the whole point. But you can’t just say “let’s improve our site’s UX” any more than a business can say “let’s make more money.” It’s the strategies you use to create your UX, namely the UI, that can enhance (or weaken) it.