For normal human beings:
UX design means User Experience, therefore, how did the visitor of your website felt, after he visited your website and most importantly, if he wanted to smash his keyboard or not. UX design should be the beginning of every website creating process because you can have a really beautiful website but what’s the point, if the visitor didn’t find what he was looking for. And it shouldn’t be only beginning, it should also be an end, because ideally, you want to measure if the visitor got where you wanted him. UX is an enormous field from setting up a buy button to creating the whole structure of a website.
UX self-thought, got experienced with Human centered design, creating wireframes, Scatch design, user research, Google Analytics etc.