management games are just that... management game. the purpose is that you take controll of a team (many, many nations and divisions to choose from)and become, essentially, the manager.
the game is realistic as much as it can be. you choose the training, you choose the players, you can buy, sell, choose player's contracts, basically like you would in real life. you play matches like you would in real life. you also create a tactic for your players to play by, and you can get very intricate and detailed at this point, choose playmakers, even tell the players how and where they should move and what kind of passes they make. then, you enter the match. you don't play, literally. the game plays out according to the tactics you and the opponent placed. you're not controlling the players, as much as they are following orders based on your tactic.
since you heaven't played any of these managment games... the only thing i can suggest is actually trying one... CM 03/04 is the best one out there right now (also the newest one) however, within a very short period of time (2-3 months) new games will come out. The people who made the CM series split up, and created 2 different versions of the CM game i told you about (there have been numerous CM games... CM2, CM3, CM01/02-my fav, and the most recent one CM 03/04. those are just some, not all) there will be 2 versions of the champion manager series coming out, one is called Champion Manager 5, which is created by Edios, and the other is Football Manager 2005, made by Sports Interactive.
Many of your resident CM experts (Trod, dave, ruud) believe that FM 05 will be by far the better game, because it will build upon the CM03/04 game i mentioned earlier, which is very good to begin with. the CM5 game does not look to be so good, at least in the beginnin, since the developers kind of had to start from scratch.
there you go, i tried to explain as best i could, but if i only confused you, PM one of those guys i mentioned, they know a hell of a lot more about these things then i do. the only thing i can concretely say is that these managment games are really fun.