The Steam Family Sharing feature allows Steam users to share their library of games with up to 5 other users, under the restriction that only one user may be playing a game from a particular library at once.

The Steam Family Sharing feature allows Steam users to share their library of games with up to 5 other users, under the restriction that only one user may be playing a game from a particular library at once.

More information can be found on the Steam Family Sharing FAQ.