I take it you are talking about hollow ground blades.......
Right ... a hollow grind is like that found on a cut-throat razor ... so the blade is very thin and light but not very strong at the blade edge. The edge bevel concaves inwards toward the blade edge.
The other usual types of grind are 'flat ground' where the blade is flat to the edge, and 'convex ground' where the blade is curved to the edge.... like an axe.
see
http://www.atar.com/F-blades.html for more infomation and pics of different grinds.
Hope this helps....
Ed