In my opinion you don't need any art skills to get started in frontend, but it does help to know some basic concepts like color theory and how to draw attention. that being said, you can absolutely get by without any prior skills in design
in terms of web stuff, frontend is the website you see and the backend is the bit that does things like store user information and hold files
in terms of general software, frontend is the actual app you have running on your pc/phone and the backend is the company's system that keeps track of your info
take discord for example
the frontend is the app you are running
that's stuff like the color scheme, the logic for how the app should run, the layout and things like that
stuff that stays the exact same unless discord update it.