http://us.battle.net/sc2/en/blog/3250656#blogWe’ve replaced the previously available StarCraft II: Wings of Liberty demo with the recently launched StarCraft II: Starter Edition. StarCraft II: Starter Edition allows anyone to play the following content for free (all you need is a Battle.net account and Internet connection):
The first four missions of the StarCraft II: Wings of Liberty single-player campaign, including Mar Sara 1-3 and the choice to embark on Tychus’s first mission or Dr. Hansen’s first mission.
The first two Challenges: Tactical Command and Covert Ops.
Access to the terran race in Custom Games and Single-Player vs. AI.
Access to the following custom maps (map selection may rotate over time):
Xel’Naga Caverns
Shattered Temple
Discord IV
High Orbit
Any campaign progress and achievements you earn while playing StarCraft II: Starter Edition are automatically saved to your Battle.net account, and will carry over should you ever upgrade from the Starter Edition to the full version of StarCraft II: Wings of Liberty.
If you’re thinking of getting into the game or know a friend who's been interested in joining you in the Koprulu Sector, it's easier than ever to give the ultimate real-time strategy experience a spin. Just head over to the Starter Edition page here, or log in to an existing Battle.net account.
For more information and a full list of restrictions, check out the StarCraft II: Starter Edition FAQ below.
Follow the link for FAQs about the Starter Edition
Basically you can play the Terran Race in Multiplayer Custom Games on a few selected Maps