A gladiator is a person forced to fight for the entertainment of others, usually to the death. This was very popular in the times of ancient Rome.
(thought I'd throw in a definition for all those who are confused by all the movie references)

I may be simple, and I may be violent, but I thoroughly enjoyed this movie. It made me question the things we find entertaining, even in our "civilized" society. At it's time, Rome was the height of civilzation, and yet they found these barbaric gladatorial combats to be highly entertaining. Traces of these competitions can be found in professional sports today.

I think the movie did a fantastic job of forcing to ask this question, even asking the question, "Is the reason I came to see this movie because I enjoy the violence?"

And on the technical side, the acting was quite good, the visual effects were fantastic, and even if you don't see the movie, check out the soundtrack with music by Hans Zimmer and Lisa Gerrard. It's one of the most exciting and moving scores I've heard in a while.