its where you go to this website, Geo Caching, and look for your area (youd be suprised how many people do this and also plant geo caches) and it ll tell you what caches are on your set radius and the hints and cooardinates to it. I myself prefer to just be lead to the area (usually by my brother) and then use the hints (much like waht youre doing) its much more fun this way. When we went to Yellowstone this was a fun break as were cruising. Be aware some pople get really addicted, i myself prefer to just go whenever .
Edit: i forgot to metnion the important part,
Each cache is usually camoufloged to its surroundings and soemtimes very hard to find. Its always funny to find the hard ones cause often times you glance over 'em a 100 times. The caches usually contain soemthing you can trade soemthing else for (ive gotten knives, collector coins, etc.).
Geocaches are usually set in a area with a scenic view or any other area of importance.
Some examples of caches ive found,
a key holder (these are called micros that just contain where you put your username down) that was tied to the inside top of a top to like a fence, like those little ball things that can pop off.
A birdhouse that was full of bird feed that had a cache hid in it.
A eletrical box mounted to a pole that had a fake wire running into the ground, inside the eltrical box was a micro.
Heres wikipedias explanation, Wiki- Geo Caching