It's pretty much like a high tech treasure hunt. I've been caching for... well.... lemme go check my profile on that site. Been caching since early 2004.
Anyone interested in starting to cache, I'd suggest you go over to the forums at geocaching.com and see if anyone is selling an old GPS so you don't spend loads of money. Many times when the newest thing comes out, people will buy it and have an old one or two GPS's they don't need. Or you can go to Bass Pro
shop. They have a very nice GPS for $100. Forget the name... it's not a Garmin or a Magellin. But I read the booklet for it and it does everything I need my Garmin 76csx to do, but loads cheaper. Wish that was out when I bought my 76 and I'd have saved several hundreds of dollars.