Steam is primarily intended as a means for downloading and playing games on a computer, but Valve has extended that further over the years--Steam Link allows you to stream games to a TV over your local network. Valve is now taking that concept one step further by ditching the hardware and bringing the games to your mobile device.
Valve has announced plans to launch two new apps in the near future that will make your Steam library even more valuable. An app version of Steam Link launches the week of May 21 and allows you to stream games to Android and iOS devices. On the Android side, that includes phones, tablets, and TVs, while supported iOS devices include iPhones, iPads, and even Apple TVs.
A beta will offer only Android support at first, and your device will have to be connected to the local network through either a 5Ghz wireless or wired Ethernet connection. You'll be able to use the Steam Controller, MFI controllers, and other devices to play.
The Steam Link app will be followed "later this summer" by a Steam Video app. This will allow you to watch the movies and shows sold by Steam (yes, Steam sells those--and productivity software--too) on the aforementioned devices. As latency is much less of a concern, you'll be able to stream video over Wi-Fi or LTE. Valve says it will also support offline playback.
It remains to be seen how well these apps will work, but if they're up to snuff, it could turn out to be a very nice perk for those who already use Steam.
Info from Gamespot.com