So what is it exactly?
Geocaching is an entertaining adventure game for gps users. The concept is individuals set up 'caches' all over the world and share their coordinates online so others can find the hidden cache. If you do take a reward from the cache you must leave something else within the cache.
So how easy is it?
Each cache has a different difficulty considering the terrain, distance and how well hidden it is. Most caches are family friendly but some will definitely, 'bring out the sweat!'
Step 1: So how do i start?
I've been using a etrax legend by garmin and highly suggest it, but consider your options and heres a mini guide about gps recomendations taken from http://www.geocaching.com/about/buying.aspx
Feature considerations for good geocaching GPS gear:
Basemap. This is highly recommended. The additional cost is marginal, and the increase in the equipment's usefulness is substantial.
Channels. Use a receiver with 12 parallel channels. This should include most manufactured after 1997. Older, single-channel receivers are much slower and may not be as accurate.
External antenna jack. This allows the equipment to be mounted inside a vehicle. It is not always possible to obtain good satellite coverage through a front windshield. Even backpackers will benefit from the ability to safely store the receiver inside a pack with an antenna attached to backpack shoulder straps.
Interface. If using the receiver with a computer, be sure that it includes both data in/out ports, and make sure it's NMEA compatible.
Memory. This is used to load detailed topographic or street-level digital maps into the receiver. Topo maps use up a great deal of memory. Capacity should be at least 8 megabytes, or the receiver should include the ability to accept a memory card for as much memory as needed.
Power source. Use a cigarette lighter power cable whenever possible. If you're only using batteries, make sure to carry spares and use a solar charger for extended field use.
Rocker keypad. Using a receiver without a rocker keypad is like using a computer without a mouse.
Screen size. For visual ease of operation, use a receiver with the largest screen that can be realistically carried. Screen size is measured diagonally. Color is great and helps define map features, although it does burn battery power.
Waterproof. Sooner or later the gear will get submerged. Get gear that is at least water-resistant. Plastic bags and boxes give electronics a little additional protection.