Trailing stop
A trailing stop is a stop-loss that follows the price by itself at a set distance. Price moves your way, the stop moves up. Price turns around, the stop stays where it was.
This locks in part of the profit and saves you from moving the stop by hand. At some brokers the trailing stop lives in the terminal itself, so the platform has to stay running.
Example
You bought at 1.1000 and set a 20-pip trail. Price rose to 1.1050, so the stop moved to 1.1030. Then price fell to 1.1040, and the stop stayed at 1.1030.
What not to do
Do not set the trail too tight. Normal market noise will knock you out of the trade. Check the volatility first.
WEEX
FxPro
Vantage