It’s a high tech Easter egg hunt. Someone hides a container of inexpensive knickknacks – a cache. Then they post its latitude & longitude on the internet, and other people go hunting for it. If they find it they trade knickknacks and sign a log to record their visit. The minimum you have to have to play is a handheld GPSr (Global Positioning Satellite receiver). Global Positioning Satellites are used in all forms of navigation today. They send signals that these receivers use to figure out where on the surface of the earth they are.