You will be taken out of a trade at the last place your trailing stop was in the event you reverse the price movement. Your broker or automated system adjusts your stop loss as price moves in your direction. If you have a trailing stop of 20 pips and you're up 60 pips, your stop loss will be at 40 pips profit (gain). You have moved your trailing stop to 80 if you go up to 100 pips profit because it trails 20 pips behind you (or whatever you set it to).