It's basically an adult treasure hunt, except instead of treasure you find trinkets or leave your name on a slip of paper. Just right here in the Springfield, MO area there are thousands of locations.
From my (very basic) understanding anyone can leave behind a box, old pill bottle, mark the location on the geocaching site and BAM it's there for anyone to find. To find the locations you just have to enter your zip code on their site and it will show you all the cache's in your area.
Of course the second that I found out about it, I HAD to go find one. There are about a dozen or so near our local Finley River so we headed there. I downloaded the free app from my iPhone which worked amazing. Once we pulled up to the park, we did a quick search on the app, it pinned three geocache's that were close - easy peasy.
Next we just followed the direction the compass on my phone pointed as it counted down the feet, by 50 yards away I was giddy like a kid. This one was called the "iron giant" so Mr. Arkansas declared that it would be on something "large".
Then BAM I saw it, the first one was pretty easy I'll admit and I'm really looking forward to finding the ones on hiking trails that are off the beaten path. We didn't "trade" any items I just added my signature to the list.
There are about a dozen hidden in the Busiek Forest that we've hiked three times now - now I have a reason to hike them again :o).
So tell me have I been hiding under a rock, have you heard about this?