basic premise behind a trailing stop is to let your runners run. The tradeoff is you will never sell the peak (doesn't seem like much of a trade off for me as I never have once timed a peak lol)
Here is how it works:
for a normal stop order: you can place an order that says "sell when it hits this price". So for you, that might be 15 or something. 50% gain.
So if the stock never goes back down to 15, you never sell. If it goes back to 15 intraday, your brokerage sells your shares for as close to 15 as they can get. The big risk here is a large premarket or after hours gap, but this is the premise.
A trailing stop adjusts that price you will sell for if the stock continues to go up. Easiest way to explain is an example
Let's say you put a 20% trailing stop on a 20 dollar stock.
Initially this means if the stock hits 16 dollars, you sell. But what if the stock rallies 100% up to 40? Then your stop loss is adjusted with it. It ratchets up to 32 (0.8 times 40). Now if it goes down to 35, your stop remains at 32. It will not change until it breaks above 40 again at which time it will ratchet up again
Something to consider for runners!