While it's engaged in streaming, no one will be able to use the original PC serving games through In-Home Streaming. "No, your computer is dedicated to running the game and input is coming from both the remote client and the local system. It would be very confusing if someone were trying to use the computer at the same time," the Q&A reads. In addition to that, Internet streaming is "currently" not supported. You'll have to rely on local network streaming to enjoy the functionality when the beta launches before year's end.
Steam In-Home Streaming is one piece of a three-pronged solution Valve has proposed for getting PC games into the living room. The company hopes to create an open gaming network, combining streaming with customizable Steam Machines and a Linux-based SteamOS. The In-Home Streaming beta will be opened to random Steam users pulled from the In-Home Streaming community group.