Overview:
Modern Warfare is back. The best-selling first person action series of all-time returns with the epic sequel to multiple Game of the Year award winner, Call of Duty®: Modern Warfare 2.

SAVE YOUR NAME, SAVE THE WORLD
Prepare yourself for a cinematic thrill-ride as only Call of Duty can deliver. Engage enemy forces in New York, Paris, Berlin and other attack sites across the globe. The world stands on the brink, and Makarov is intent on bringing civilization to its knees. In this darkest hour, are you willing to do what is necessary?

SPEC OPS
Special Ops returns with a bevy of additions, including 16 new objective-based missions and the all-new Survival Mode. Team up online, locally, or play solo and face endless waves of attacking enemies throughout every multiplayer map. Purchase and customize your weapons, air support, equipment and abilities to stand up against increasingly difficult forces and land a spot on the leaderboards.

Earn experience and rank up with the newly implemented progression system. The higher the rank, the more weapons, air support, and gear armories you will have available to customize so you can change your tactics on the fly. In addition to the action packed battle for freedom, the cooperative Survival Mode also serves as an effective training tool for competitive multiplayer action.

MW3 MULTIPLAYER IS BIGGER AND BETTER THAN EVER BEFORE
Modern Warfare 3 delivers a multiplayer experience that continues to raise the bar by focusing on fast-paced, gun-on-gun combat, along with innovative features that support and enhance a large variety of play-styles. Now, you can truly define your approach with a toolkit more expansive than any previous title.

Killstreaks have been redesigned, new game modes are being introduced, and a gun progression system evolves your weapons over time. Along with new perks, 16 maps and enhanced private match customization, multiplayer has been completely rebalanced and polished into the most intense and rewarding experience possible.

Source: official Website