DISCLAIMER: This game has some elements that are not for kids, mostly the sprays that can be customized by players, the small amount of language from some characters, and cartoonish gore (it's mild, but not as mild as CS:S or Halo since the body explodes).
Ok, this game is AWESOME. Mostly because people who normally try to go Rambo and kill everyone on the opposite team will not fair well. As the name implies, this is a team game that relies on everyone to develop strategies to defeat the other team.
Say you're playing a game of CTF. You choose a scout, the fastest but lowest health character to quickly get to the flag. UH OH! An engineer has built a sentry at an entrance. You see a team spy heading up and you take cover so he can stealthily zap the sentry. Wait, why he's heading over to you, and why'd he just turn invisible? *STAB!* It was an ENEMY spy disguised as one of your spies, oh noes! That's ok though, as a soldier just rocket jumped up to a ledge and took out the sentries with his rockets. You get down to the flag room, and your teammates (a Medic and Heavy) come down with you. Oh no, there's demoman bombs in front of the flag, waiting to be detonated when you enter! BUT WHAT'S THIS? The medic has healed the Heavy so much that his ubercharge is now full! He activates it and he and the Heavy go in and tear the Demoman apart with bullets! You grab the flag and quickly run back to your base. But a pyro lights you on fire with his flamethrower as you're running out! THEN HE GETS SNIPED BY YOUR SNIPER! OH, YOU GET THE FLAG IN AND SCORE, SWEET!
And that's just one way it works, the 9 classes (Offense: Scout, Soldier, Pyro/Defense: Demoman, Heavy, Engineer/Support: Medic, Sniper, Spy) can be used interchangably for the various gametypes and situations you might encounter in the game.
The best thing is that each class is balanced with the other. Scouts are the fastest but can't take too many hits, while the Heavy has alot of health but can barely move. In order to make up for weaknesses, you have to combine classes to increase your strength (A spy disguises himself to take out the sentry with a zapper, then the soldier immediately shoots it down before the Engineer can fix his sentry). There's so many awesome things to this game. So if you're able to, you really should get it.
