League of Legends is a free to play player versus player roleplaying game in the form of a real time strategy. You control a single unit, or hero, and battle for victory with your team against your opponents. You can play 5versus5 or 3versus3 matches.
The idea of the game is to advance along 3 different lanes and destroy your opponent's defense towers. Escorting computer controlled minions and using them as a meat shield you can wreak havoc on these towers and gain access to the enemy's base. Of course it's not as simple as it sounds. The enemy team won't just let you destroy the towers and will fight back by destroy the ones you have. However once you've gained access to the enemy's base most of the players I've played with seem to think the game is over and just surrender cursing what a “noob” team they have. The joke’s on them because they themselves are a part of that team. The game ends after you've successfully destroyed the enemy's Nexus or they have destroyed yours. You gain points by playing and with these points you can “purchase” hero’s for your profile. Alternatively you can also buy your champions with money if you’re that desperate.
There's a wide variety of characters you can choose from and each one is unique in their own way. My advice is pick the one that seems best suited for your gaming style (melee, caster, ranged etc.) and stick with it. You need to familiarize yourself with one character in order to be good in the game. If you keep changing your hero all the time you’ll end up losing.
Like I said it’s free to play even though it comes with the cost of having to listen to all the whining and moaning of your immature teammates. I recommend you try it if you're interested in player versus player fantasy rpg games. I also recommend you befriend yourself with some people and play with them, because if they call you a "noob" you'll know where they live and if need be you can beat the crap out of them for pissing you off.