Steam Family Sharing has been a thing for 10 years now. Steam Families is a new thing that works differently. Family Sharing required you being logged into every PC where you want your library to be shared with other users. It also made your entire game library inaccessible to people you share with if you or someone else is playing a game from your library. Only one person gets to play your library at a time. Steam Families behaves differently. It's currently only available in the "Steam Families" beta branch for the Steam client. Once you opt in, you will have the option to create a "Steam Family" where you can invite up to 5 of your Steam friends to join as long as they are located in the same country as you are. Once everyone has joined your family, everyone's games gets shared with each other and combines into a larger game library. Even if you are playing one of your own games, anyone else can play any of your games except the one you are currently playing. If multiple people own the same game, then the amount of copies of that game become available for multiple users to play. For example, if 3 people in your family own Portal 2, then any 3 people in the family can all play it simultaneously whether or not all of their accounts own the game. Answer from Moskeeto93 on reddit.com