A "Trailing Stop" applies a special algorithm to a Stop Loss order. When a Trailing Stop is placed, the level of the Stop Loss will change along with price movement. If you open a Buy position, and the price of the instrument increases by a certain number of points, with a Trailing Stop, the level of the Stop Loss will increase as well. If you open a Sell position and the price of the instrument falls, a Trailing Stop order will cause the level of the stop order to decrease as well. Generally speaking, a Trailing Stop causes the level of the Stop Loss to trail the price level.
Here's an example of how this works:
Please note that a "Trailing Stop" order is managed by the client's trading platform, whereas Stop Loss and Take Profit orders are controlled by the server. Accordingly, a Trailing Stop order will only remain active when MetaTrader is running and connected to the internet. Once you close MetaTrader, your Trailing Stop order will be deactivated, but your Stop Loss order will remain active, assuming it was placed earlier than the Trailing Stop.