A stop loss is a trading function which can be used to automatically sell your crypto/stock when the current price goes beyond a certain number. Traders use this to manage the risk of unexpected price movements. Basically it is as it sounds, it "stops loss".

But I have found that stop loss is not worth it in most cases, in the world of cryptocurrency. Because cryptocurrencies are just too volatile. You will just be losing money if you put stop losses without a big enough spread, because even Bitcoin can go up/down 10%+ in a matter of minutes....