Ollie, there are Stop Losses and there are Trailing Stops. There's no such thing as "Trailing Stop Losses".

Stop Losses provide a means of limiting your losses should a purchased stock drop in price after your buying it. They are set before buying and are never moved. They could perhaps be a fixed percentage or $ amount below your purchase price, but the best place to position them is just below a recent support level.

Trailing Stops are a type of exit strategy. They are based on the latest shareprice and rise as the shareprice rises. Most commonly they are based on a fixed percentage of the highest price, but there are many other ways of setting them. They are never lowered. Their purpose is to lock in a proportion of your profits should a stock you are holding make a significant fall from its highs.

While "fixed percentage" or $ based Trailing Stops can act as a standalone exit strategy, generally speaking they significantly underperform other indicators.