Geocaching is a healthy outdoor activity, a modern, hi-tech hide-and-seek. Geocaches are hidden, often in interesting or attractive places, and the location is published on a geocache listing site. Other cachers then use a GPS receiver to try to locate the cache. A cache should have a log book, which the finder signs. The find is then logged online, on the listing site. This maintains a record of your caching activity and provides feedback to the owner of the cache.
Caches traditionally are large enough to hold a few small and inexpensive "trade" items, though the modern trend is towards smaller caches. A finder may choose to take an item and replace it with something of similar value. Caches may also contain "trackables", small objects or geocoins, which are moved from cache to cache and tracked on the listing site. Caches may be camouflaged to blend with the surroundings, or even disguised as other objects and left in plain view. Particularly in urban areas, caches may be much smaller to reflect the difficulty of hiding a large plastic box in a busy place.
Within this framework there is a wide variation of style and preference.
Some people enjoy the challenge of finding caches in busy urban areas, whereas others prefer quiet woodlands or remote moors and mountains. For some people the game is largely about the numbers and statistics, and they may try to find a hundred or even more caches in a day. For others the quality and depth of individual caches is of greater interest, and in extreme circumstances they may spend a day or more finding just one. Most are somewhere in between.
Many enjoy a walk in the country where the caches set the route. Another group enjoy the challenge of finding caches in places that are hard to reach, such as underground, up in a tree or on an island. Most cachers enjoy that geocaching takes them to places they otherwise would not see, or even be aware of.
Many people cache alone. More commonly we go out with family or friends. And there are geocaching "events" where we can meet other geocachers to chat about our common interests.