Trackable geocaching coins each have a unique tracking ID of some sort. With this ID, you and anyone who finds a trackable coin to log on to the corresponding website, enter the tracking ID and log the or view the latest location of the coin. Trackable geocaching coins can make for an interesting class project or just add to the enjoyment you get from geocaching.
If you find a geocaching coin, look for a web site address on it as well as a tracking ID. Many geocaching coins are trackable at Geocaching.com, so you may want to check there first, but not all geocaching coins can be tracked there. When you go to the correct site, it will provide you with instructions on how to log where you found the geocaching coin. Then you can take it on your next geocaching hunt and leave it for someone else to find and log.