They actually only work for mechanical keyboards...and probably not all of them (this keycap remover is designed for Cherry keycaps and their clones, other manufacturers might have different designs that need different removers). Don't try this on the normal keyboards you get from the office or something, most of them aren't designed for this and it might be very hard to put them back in place!

But the good news is that for normal keyboards you can just get a sticky gel ball (I'm not sure what it's called) and just roll it over the thing to clean it up :) Mechanical keyboards' switches are quite fragile to non-downward forces compared to other keyboards so we need these tools to perform cleanups.

Yes, there are a lot of keyboards! Probably this Wikipedia page can help :)

P/s: Thanks for the resteem!