You can find out all you really need to know about Geocaching here http://www.geocaching.com/
Description from homepage of above site:
Geocaching is a high-tech treasure hunting game played throughout the world by adventure seekers equipped with GPS devices. The basic idea is to locate hidden containers, called geocaches, outdoors and then share your experiences online. Geocaching is enjoyed by people from all age groups, with a strong sense of community and support for the environment.
So today I decided to try and locate a geocache or two. First I checked out the site for caches near me. To do this you go to 'hide and seek a cache', then under the 'seek' section go to 'by country' and scroll down to your country. In my case, United Kingdom. Then you can choose your state/province, in my case, West Midlands. Then, hey presto, you get a list of all the caches hidden in that area. Now, if you want to start a little closer to home you can click 'new search' and pop in your postcode.
Then it's a case of picking which cache or caches you want to go and look for. They all have a rating in two parts. The first is for 'difficulty' the second is for 'terrain' and both are scores out of 5. So, 1/1 would be the easiest and 5/5 the hardest. It's best to start with 1/1
Before you go out looking you need to note the co-ordinates of the cache. You can download these straight to your GPS but as mine is not so up to date I had to add them manually. If you don't know your way around your GPS device very well, then now is the time to learn. I thought it would be easy but I had to really mess around with all the settings to get mine to work properly. It kept sending me back to the main roads!It's also advisable to get as much information about the cache as you can. If you are new then you will definately want all the clues and have a good look at the maps. It looks easy but it's not. I'll explain all in my next post, my first adventure.