It's a very competitive and fun "eSport" section of BO2, especially if you're into the MLG/GB scene. I personally am not with LG or GB, but I do play league play. You can use any class (Everything unlocked) and you get 7.5k to 10k XP each game. I went from Prestige 1 level 15 to Prestige 2 43 in one night just trying to boost my level in LP.
There are 6 Divisions, and you are placed depending on how you do in your 5 placement matches. They are as followed: Iron, Bronze, Silver, Gold, Platinum, Masters. Masters being the best, Iron being the worst. In Season 1, I started at Iron division because I didn't know how it worked, but after a 40 winstreak, I ended up in Masters in the first week of the season. I highly recommend you try it out, and feel free to message me on Xbox if you'd like. My gamertag is Handguns.