PSA: Call of Duty: Modern Warfare 3 Multiplayer is playable in OFFLINE Local Mode now. Activision is DMCA-ing all content that is shared, but if you want to get a head start of some of the maps, see the weapons.. etc. It works.

Call of Duty: Modern Warfare 2 has three different game modes: Campaign, Spec Ops, and Multiplayer. Campaign is a single-player mode where the player completes eighteen levels connected by an overarching plot.