Geocaching is probably best described as a modern treasure hunt with GPS equipment.
There are people (Geocachers) who hide a container with a logbook somewhere and then publish the coordinates of this "cache" on the Internet. Other geocachers use these coordinates and their GPS devices to hunt down this hideaway, entering their nickname and date in the logbook once they have found it. Afterwards, the cache is put back in the exact same place it was discovered,... for the next geocacher who comes along. Once back at home, the find is logged on the Internet along with a short commentary.
Geocaches are stashed away worldwide. On mountains, in forests, parks, but also in the heart of towns and cities.
What's behind the fascination of this worldwide scavenger hunt? Perhaps the fact that Geocaching is all about having fun, the fun of being out and about, the fun of searching and of teasing your brain a little. The fun of a challenge. And the fun of interacting with other Geocachers - through those logbook entries, through related websites and forums, as well as meets known as Event Caches.