How a trailing stop works
A trailing stop is a stop-loss that moves in your favour as the trade goes your way, but never against you. If you are long and set a trailing stop a fixed distance below price, the stop rises as price rises, locking in more of the gain, and stays put if price falls.
The appeal is that it lets a winning trade keep running while automatically protecting profit already made. Instead of choosing a fixed target, you let the trade continue as long as it keeps moving, exiting only when it pulls back by your chosen distance.
The core tension
The difficulty is setting the distance. A tight trailing stop locks in gains quickly but gets triggered by ordinary noise, ending the trade early before a bigger move. A loose one gives the trade room to breathe but gives back more profit when the move finally reverses. There is no perfect setting, only trade-offs.
A concrete way to see it: trail too tightly and a normal retracement stops you out just before price surges again; trail too loosely and you watch a large paper gain shrink substantially before the stop finally triggers. Choosing the distance is a judgement about how much noise the instrument makes.
Its limits
A trailing stop shares the same limitation as any stop: it is a trigger, not a guaranteed price. In a fast gap, the actual fill can be well beyond the stop level, so it protects less than the number suggests during violent moves.
Used sensibly, a trailing stop is a useful way to manage a winning trade without watching it constantly, and to take the emotion out of exiting. But it is not a magic profit-lock. Like every risk tool, it manages risk rather than removing it, and it works best when paired with realistic expectations about how price actually moves.