Steam Family Sharing, a new service feature that allows close friends and family members to share their libraries of Steam games, is coming to Steam, Valve announced. Steam Family Sharing is designed for close friends and family members to play one another's Steam games while each earning their own Steam achievements and storing their own saves and application data to the Steam cloud. It's all enabled by authorizing a shared computer.
Once a device is authorized, the lender's library of Steam games becomes available for others on the machine to access, download, and play. Though simultaneous usage of an account's library is not allowed, the lender may always access and play his games at any time. If he decides to start playing when a friend is borrowing one of his games, the friend will be given a few minutes to either purchase the game or quit playing.
The Steam Family Sharing feature will become available next week, in limited beta.