The game really has no part of the story that surrounds it. There's no real narrative to tie things together. It's just a series of six-on-six matches with simple objectives like "control the point" or "escort or attack the objective." Each quick play session only lasts about twenty minutes, and even when I lose I still have fun (although being in a group that doesn't work together is frustrating).
There are a wide variety of characters to play, each with her or his unique play style. Part of the fun is picking a character that complements the other characters on your team and working together to achieve the goals. While there is some space for people who like to just go on their own to eliminate the other side's characters, the game rewards group efforts more than lone wolf tactics.
I would not have chosen this game on my own. I'm glad that Alex gave it such a glowing recommendation. Sometimes it's good to play games outside of my normal comfort zone.