It's called Geocaching and it goes something a little like this.
Imagine the Easter Bunny was real, but instead of a bunny it was thousands of strangers all over the world, and instead of hiding chocolate eggs - because lets be honest, what was a bunny doing with eggs or chocolate in the first place? - it's containers of various sizes that hold no more value than the personal satifaction of finding them. Add in a bit of gps gadgetry and cryptic clues and thats geocaching.
These thing are everywhere, literally. You know that tiny hole of a town you live in? There is probs one there. That park you used to play in as a kid or the car park you visit every week to do your shopping? Bet there's one there too.
These pictures would totally make sense if you were a geo-nerd*
The Big Ev is on the hunt. Current tally: 9 found.
*Not an actual acceptable term for a Geocacher