in a trade, stop loss is used to anticipate if the market moves not according to what we planned, with the stop loss the transaction will close automatically, so we don't get carried away with bigger losses. especially if we can't always be in front of the computer, then this can help traders to survive
By now everyone already must know the meaning and it would have been much more worth if you shared your experience of using it or not using it, instead of explaining what it is. The name stop loss itself suggests what it's meant to do.
I trade a lot of coins during a bull run and during those times I use it to make sure if I lose the track of a few coins, I don't end up paying it with my wallet, at least not by too much.
Lots of traders often criticize stop loss function because it takes away the possibility of recovery but I don't know if even 10% of coins that go down ever recover unless a certain Elon Musk is sitting behind to help it.