The app is based on a very simple principle: some users hide treasures around their city, and write a short set of instructions with their correspondents about how to find it. Meanwhile, other users try to find the treasure using the supplied clues.
As you might imagine, the nature of the treasure itself depends on the users. You might find a handwritten note inside a plastic bottle, or stumble upon a book or old game. It all depends on what you and the other users around you decide to leave.
To use the app c:geo, you'll first need to register on the geocaching website, which you can do from within the app itself. Once that's done, all you need to do it select which treasures you want to find, and get started on your adventure.
c:geo is a simple app for a complex service. Geocaching is an activity that changes depending on the users involved, so while it might be disappointing for some, for others it can be a truly thrilling experience.