This is the original cache type consisting, at a bare minimum, a container and a log book. Normally you'll find a tupperware container, ammo box, or bucket filled with goodies, or smaller container ("micro cache") too small to contain items except for a log book. The coordinates listed on the traditional cache page is the exact location for the cache.

The general rule of thumb is, "If you take an item, leave an item, and write in the logbook." Some caches are themed, so make sure to read the description before going on a hunt.