Valve has announced an interesting new feature to Steam and that is the ability to livestream your games to your friends. You may want to show off or your friend might be stuck on a certain part and you want to show them what to do. Whatever the reason this feature can be added to the list of "things Steam has that make it awesome."
This feature is available right now to Steam beta participants.
When you see a friend in game, simply click on "Watch Game" from their profile or from the Steam Client Friend's List to open a window into their gameplay -- no game ownership, special fees, or additional apps required.
For more information visit the official page: steamcommunity.com/updates/broadcasting