It's a hardcore sim/management title in which you take the role of manager for a football (we call it soccer here in the States) club. Your duties extend across every facet of the game, as you control things like tactics (whether your players play aggressively or defensively), squad rotations and even player trading.
In the case of that last item, you'll need to manage salaries and scout players suitable for your club, while simultaneously putting those who aren't quite gelling with your team onto the training block. You have to manage your management.
Overall, Football Manager is a decent way for hardcore sports sim fans to scratch that itch -- it provides all of the control most traditional console-based sports games offer via their franchise modes, just without all of the flash. From a functionality standpoint, the game can easily hold its own next to the big boys.
Football Manager 2010 (Sega, $9.99):