Steam’s Family Sharing feature lets you share your game library with your friends and family.

Steam Steam Family Sharing is now available to all Steam users

Valve has finished beta testing the Steam Family Sharing feature and has now made it available to all Steam users.

As the name suggests, the feature allows users to share their game libraries with friends and family. There are a few caveats, though: You can only share titles that do not need an additional third party key, account, or subscription in order to play the game. Also, you cannot choose selective titles to share in your game library. When you share your game library with a friend or family member, your entire collection of games will be shared.

You have the ability to authorize five friends or family members to share or borrow your library at any given time. The borrower will have access to your titles, but not to your saved games. Their game progress will be saved in their own saved game file. However, a shared library can only be used by one user at a time. If you’re the owner of the library and decide to play a game when one of your borrowers is also playing, they will be given a few minutes to save their game and either disconnect or buy the title.

In addition, the Family Sharing feature lets your friends and family access games only on authorized devices. You can authorize a maximum of ten devices at any given time. Also, any region restricted content will be unavailable while lending or borrowing content. Valve has also clearly stated that any fraudulent activity by you or anyone you share your library with will ultimately result in a revocation of the ability to share games and might even lead to a ban by the VAC (Valve Anti-Cheat) system.

Source: SteamSteam Family Sharing FAQ