A clavier à lumières is a fancy way of saying a keyboard with lights. It's like a normal keyboard that you use to type on your computer, but the keys light up so you can see what you're pressing even in the dark.
Just imagine you're in your room and it's really dark, but you need to type something on your computer. Without a clavier à lumières, you wouldn't be able to see the keys on your keyboard, so you'd have to try to guess where each key is and hope you don't make any mistakes.
But with a clavier à lumières, when you press a key, it lights up so you can see exactly which key you pressed. This makes it easier to type in the dark and can also be helpful if you're a beginner and still learning which keys correspond to which letters.
Overall, a clavier à lumières is just a cool and useful addition to a regular keyboard. It makes typing in the dark easier and more fun!