Geocaching is initiated by an individual hiding a cache, normally a waterproof container with small items inside, then recording the location with a Global Positioning Unit (GPS). The cache may be in a hollow log or under an object. The individual then posts the GPS coordinates, along with a description of the cache on the geocaching website.
Other individuals then try to find the cache. When it is located, they sign a log book, then take or leave a small item. They also post their find on the online log book.