There are many different types of caches.
The most common cache is the 'traditional'- a basic cache ranging from a nano size to 'large'. The co-ordinates given will take you straight to the cache. We've found 318 of these so far. They are, by far, the most popular types of cache.
Multi-caches are a series of off set caches. The given co-ordinates will give you a clue to further clues or the actual cache. We have just 4 of these found.
Mystery caches involve a puzzle (numbers, words, poems, rhymes etc) which needs to be solved to find the cache. We have solved 9 puzzles so far.
Today I found our first 'letterbox' cache. Letterboxing dates back to 1854, it was first started in Dartmoor. See more here.
We've also found a 'virtual cache' which doesn't have a cache container. Some virtual caches require you to email the cache owner with an answer specific to the co-ordinates given.
There are a few other types of caches, but we are yet to do those.