You type in the YouTube url. The video is then loaded into TubeChop. You can then cut out parts of the video so that you are left with the relevant parts you want to use. You then have the embedding code which you can use or you also have a new url that you can use (the url is no longer a YouTube link but now is a TubeChop link).
Here is an example of one I have chopped some off.
The new url is: http://www.tubechop.com/watch/182695