Trailing stops allow you to lock in gains while leaving the trade open until the price of the instrument reaches your trailing stop level or a take profit limit (if you have set any). The stop-loss order is executed, and your position will be closed when the market price hits your trailing stop.
If the market continues to move in a favoured direction, so does the trailing stop, which maintains the stop loss at a predetermined distance from the current price. When the market stops moving in a profitable direction, the trailing stop doesn't move.
If the market price moves in your favour but then reverses, the trailing stop will not reverse. If the reversal goes through the trailing stop, the position will be closed, either limiting your loss or locking in a profit. This means you can step away from the computer screen and have confidence that your positions are being properly managed.
Example of a trailing stop
Let's understand this with an example:
You have a long position on the EURUSD at 1.1250, and you put a trailing stop 100 pips below your opening price. The trailing stop will shift (or trail) your open position to the upside with each pip movement. The trailing stop will be moved to 1.1151 if the market price rises to 1.1251. The trailing stop will move up to 1.1180 if the market price hits 1.1280.
Nevertheless, if the price reverses after reaching 1.1280, the trailing stop will remain at its most recent level of 1.1180. Trailing stops, as you can see, automatically lower your potential loss when compared to regular stop-loss orders since they tighten with each new favourable price tick.
Lastly, if you're wondering if trailing stops can expire, they have no time limit. You may keep them active indefinitely, although they are automatically cancelled when your position is closed.