In reply to bjoe:
The official UIAA verbal definitions are:
Grade I: Minor difficulties. Easiest form of rock climbing (not easy walking terrain!). The hands are necessary to help stay in balance. Beginners must be led on a rope. A good head for heights is necessary.
Grade II: Moderate difficulties. Climbing with simple hand- and foothold combinations (technique using three points of contact).
Hope this helps!
Edit: typo
Post edited at 13:29