Steam's In-Home Streaming service, announced late last year, is now available to all Steam users, allowing you to stream your Steam games from one computer to another in your home.
By logging into Steam on two computers across the same wi-fi network, you can choose to remotely install, launch and play games on lower-end computers, laptops and home theater PCs, streamed directly from your other computer.
This functionality can also be used to stream games to other operating systems -- for example, a Windows-only game can be streamed to an OS X, SteamOS or Linux device.
Valve says it's as simple as logging into the same Steam account on different computers on the same wi-fi network, then selecting a game. More information can be found on the official website