Let’s make this real simple by taking an example of shopping at the supermarket.
You enter the market and see all the items stacked on shelves neatly. After browsing around the store, you enter a particular section to purchase the items you have in mind (vegetables from the fresh section, cleaning supplies from the cleaning section, junk food from its section etc.). You pick up the items, place them in your cart and then head over to billing where your items are billed, payment is made and you leave the store. In some cases, you may enter the store just to look for something really specific, search for the section it is in, pick it up and check out. And some other times, you just keep browsing around the store without really buying anything.
Sounds familiar? Let me explain now in the context of UX and UI design. The supermarket with all its items neatly placed on shelves with proper markings and sections is your UI design. How the user goes around the store, finds the items he’s looking for and how easy it is for him to do the required task, the people guiding him around the store is what is called User Experience. Designing the best experience for the user and making life easy for him is what UX Design is all about.