PS+ is Sony's subscription service that provides several member benefits including access to a rotating "instant game collection." The game's are only available to active PS+ members, and they are generally only available to download for free for a limited time (though once you've added them to your account, you can redownload the game again at any time).

PS+ is mandatory for online play in PlayStation 4 games. The service typically sells for $18 for three months or $50 for one year.