Basically, the Playstation Plus system is one that you can pay for on a monthly basis to gain access to premium features. Some of those extra features include updates downloaded automatically, early access to beta testing and store discounts on a regular basis. The membership fee that you pay also gives you access to six free games per month.
That is explained as two for each system and the membership includes 10GB of space to save up to one thousand game files. Back in 2013, Sony announced that if you wanted to play online multiplayer games with the Playstation 4, you would have to have a Playstation Plus membership.
If you are interested in the membership, which is worth the monthly free games at the minimum, you can go to the website and choose a monthly, three month or annual subscription package. Once you setup payment options and complete the purchase, your account will automatically be upgraded.