As Teirae said each of the containers are hidden. You could walk past a heap in the city every day and not know. We found a geo cache once that was a 44 gallon drum. That was a country one though LOL. Most of them have little prizes in them such as a match box car, key ring, whatever really. If you take something from the box though, you have to leave something behind for the next person.

There is also a log in each the caches that you have to sign to say you've been and then you come home and record it online on the Geocache website. Andrew's found 496 of them so far. It is a good thing to do when you're home bored with the kids on a weekend. If we do country ones we will find 6 or 8 in a day, but that will involve a lot of driving too.

To find them you do need a GPS and be a part of the Geocaching website. That way you can download co-ordinates.