That's a very raw question because stop-loss isn't the same in all the exchanges and some don't even have that option at all.

If you are asking should I use stop-loss?
I would say yes because the market swings wildly and you better have some safety in place.

Are you asking what is stop-loss?
Well, in simple words, a safety in place if things go south. For example, if you have a coin that overnight gets zeroes, you can set a stop loss price, at which it will get sold out.