A trailing stop is a stop Loss in a trade to prevent a loss to be too big; if a trader sets the trailing stop to 6 pips it means the trade will stop if the trade falls 6 pips.
I was on YouTube and found a fellow explaining the use of a trailing stop; One of the issues he talks about is how wide a trailing stop should be; watch the video and hear how he explains the use of trailing stops.
The video is available at this link as it was not possible to embed the video in this post.
