UX design is all about the overall experience of the user during and after using your product.

Using a house structure to explain better,

Questions like:

Is the living room the first room you walk into at the entrance?

Does the bedrooms have their bathrooms? Or does a visitor have to leave her room to yours to make use of the bathroom?

How is the positioning of the windows? Does it ensure enough natural light?

A UX designer is responsible for how the user feels using your product.

UI on the other hand is all about the visual layout and design of a product.

That is, the look and the feel of a product which include typography, color scheme and layout.

Using a house as an example, UI design is what make your house looks beautiful.

Things like the colour and size of your chair, the color of the walls the presence of flower verses and other accessories that makes you enjoy living in the house.

I hope this gives a better understanding.