Sharing your digital games, apps, and other downloads with your family
and friends is possible with the Primary and Non-Primary Account [...]
In this example we are using Ethan and Katie who both have their own
PSN account IDs. Ethan also has a bunch of digital games which he
bought on the PSN Store using his PSN account. Objective: He wants to
share these digital games with Katie, so this is what he does:
Both Ethan and Katie can now play the same game at the same time on
PS4 (A) and PS4 (B) with no restrictions.
Benefits of activating a PS4 as Primary:
- Anyone who uses your Primary PS4™ system can enjoy applications you
purchase from the PlayStation®Store. Other users on the system can
also enjoy some PlayStation Plus benefits from that account, even if
that user is not logged in.
- This method of sharing only applies to digital games and apps. The sharing of disc games will still require you to physically lend your discs to others.
- When you log into a non-primary PS4 with your PSN ID, you will need an active Internet connection so that games and apps from your PSN account can be authenticated by PSN.
- You can activate only one PS4 system as primary per PSN account.
- You can deactivate a PS4 system only from that system.
The whole explanation and the picture belongs to gripitaustralia.
There is an official article about activating and deactivating you Primary PS4 on playstation.com.