UI refers to the aggregation of approaches and elements that allow the user to interact with a system...
...consider user experience as the reactor or nucleus of a brand. A brand being, in essence, the sum of the experiences that a person has with a company or organization. User experience is the goal. Not just the goal of an interface, but of a product or interaction with an organization. When good user experience is achieved, every desirable or positive effect that one could possibly think of flows from it. UX is focused on success of the whole. In reality, the product is not the sum of its parts; the experience is.
