To put it simply, the biggest difference between the two is that graphic design is more about printing, and of course some of it is displayed on the screen. The simplest and most intuitive understanding of UI is that it is all about what is displayed on the screen!

To be more specific, graphic design involves some static things, such as posters, roll-up banners, business cards, and so on. UI is almost all dynamic interfaces, but what needs to be designed is a static interface. As for how to add dynamics, that is added by the front end and interaction!

Most intuitively, the things made by UI design using PS are in RGB format, which is the so-called three-color, the format displayed on the screen! Most of the graphic design made by PS is in CMYK format, which is the format used by four-color printers!

The two are actually very related. The foundation of UI design in the early stage is graphic design! For example, typesetting and color matching are all basics. When used in UI, these basics will be used to make the interface simpler and clearer, easier for people to look comfortable, easier to operate, and so on!