Just names your favorite and least favorite map packs for the game.
I personally like Forces of Nature the best, and despise Fenix Rising. Seriously, I don't like any of the FR maps. Slab was fun at the beginning, but it's wildly overplayed now. Escalation has always been bad, even in Gears 1. Anvil is far, FAR too campy. Academy looks pretty but it plays horribly in my experience.