A stop loss is a risk-management order that closes a position automatically when the price reaches a level the trader has chosen in advance. Its purpose is to cap the loss on a trade so it can’t grow beyond a planned amount. By deciding the exit point before emotions get involved, a stop loss helps traders stay disciplined and avoid holding onto a losing position in the hope it recovers. It is one of the simplest and most widely used tools for protecting capital, and a core habit of structured trading.