In reply to emmswhit:
Well for starters and strictly speaking ice climbing doesn't require snow. In fact some of the best experiences I've had, admittedly abroad, have been when there has been hardly any snow at all.
It differs from both sport and trad because it is more run out and protection can be dependant on the quality of the ice. Grades start at 1 and go up depending upon the steepness of the line and the quality of the ice. 1 and 2 are very easy angled. 3 gets a little steeper and may involve short sections of what feels like vertical. 4 and 5 definitely feel vertical and strenuous for most of a pitch and above that I can't comment.
In some ways grading is even less objective than on rock. A pitch can have lots of ascents so steps tend to develop. This can make a route feel easier than it is graded.