UI kits, what is it and what is it eaten with?

Question

Design

Hello, for a long time I can’t understand what these UI kits are and where and how they can be used? For example, this kit is www.syntaxxx.com/free-ui-kit-from-pixelkit/. It is written that it contains fonts, PSD files, etc.
Are these sets useful primarily for designers? For a front-end developer, are they of value? Except inspiration.

Answer 1

If you make the UI of an app/website/etc... and cut it to fit your needs, then it will come in handy. If you use the work of a designer who gives you a ready-made cut, then you have nothing to do with it.

Answer 2

It also shows what they are for...