It is a small tool to capture things going on an X-Windows display to either individual frames or an MPEG video. On Windows machines there are commercial tools like Lotus ScreenCam or Camtasia. From my experience, new user will take some time to take off with a video. I just think it needs more work on user-friendliness.
Where to download?
If you use Fedora, you can install with yum: yum install xvidcap
If u use Ubuntu or Debian, you can install with apt-get : apt-get install xvidcap
or for advanced user, you can download the source code here.
Below is a video off my desktop I took with xvidcap. On the video, you can see that I was showing off Compiz. :)