Devil May Cry is a game for the
Playstation 2 (with versions for other home formats quite likely to follow) developed by
Capcom. It was designed (or directed, or whatever the currently fashionable term is) by
Shinji Mikami, creator of the
Resident Evil (
Biohazard in Japan) series. The game was initially intended to be a fourth installment in that series, but was substantially redesigned to allow the developers to try some new ideas (presumably that wouldn't have fit into the
Biohazard style and storyline).
The game is an action-adventure where the protagonist, a man named Dante, has to fight various supernatural assailants on a mission to save the world from a demonic invasion. Dante is half-demon himself, and can use his super powers as the game progresses. In mortal form, he is armed with guns and a sword, allowing for lots of different moves. In technical terms, the game is a step up from the Resident Evil series, with crisp fully 3D backdrops and detailed character models. It still isn't the prettiest of games however.
In a nutshell, the game is Castlevania in 3D, using Resident Evil's game mechanics. That's a gross oversimplification, I'm sure.