Difficulty and Terrain Ratings
Geocaching.com uses a rating system to rate caches on two levels:
Terrain: rated from 1 (handicap accessible) to 5 (special equipment needed), the terrain rating lets you know what the trip is going to be like once you leave your car. Difficulty: Rated from 1 (easy) to 5 (very hard, either very well hidden, or there is a difficult puzzle to solve), the difficulty rating lets you know what the search is going to be like once you get to ground zero.
see also: How to rate cache difficulty