Valve has now opened the doors to finally allow every Steam user the ability to stream and play their Steam games across multiple computers on the same network.
Players who have multiple computers at home can immediately take advantage of the new feature. When you login to Steam on two computers on the same network, they automatically connect, allowing you to remotely install, launch, and play games as though you were sitting at the remote PC.

Steam In-Home Streaming allows you to play your PC games on a lower-end computer, such as a laptop or home theater PC, or a computer running another operating system, such as Mac OS X, SteamOS, or Linux.

When you play a game using In-Home Streaming, video and audio are sent through your home network from your high-end gaming PC to another device in your home. From here, your keyboard, mouse, and controller input is sent back to the remote computer.

That's the very basic explanation of what In-Home Streaming is capable of. Valve thankfully set up a dedicated Steam In-Home Streaming hub that can provide you with some additional details on this new feature.