You'll also get the PlayStation VR game Firewall: Zero Hour for a total of 5 games if you count each BioShock title individually.
The BioShock Collection includes all titles in the franchise: the original BioShock, BioShock 2, and BioShock Infinite.
It is unclear if The Sims 4 will come with its vast array of downloadable content, but it is unlikely - allowing people to access the base game for free is a good move to encourage sales of dlc while still providing the free-to-play crowd with a good time.
PlayStation Plus is Sony's premium subscription service that allows users to access online multiplayer mode for many titles - the monthly freebies are Sony's way of dangling a carrot in front their users to keep them subscribed.
The free games you gain with PS Plus will expire along with your membership, but will become active again once you resume subscribing.