UI is how it looks. UX is whether it works.
UI design is the visual layer. Buttons, typography, colour, spacing, layout. UX design is the strategic layer. How information is organised. How users navigate. Where friction exists and how to remove it. How a visitor moves from first click to conversion. UI determines how it looks. UX determines whether it works. Both matter. Beautiful design with broken UX produces low conversion. Sound UX with weak UI erodes trust before anyone reads a word. The best sites get both right.