PlayStation Plus was introduced four years ago as a premium subscription service that would net subscribers free games and game discounts every month. It was totally unlike Xbox Live in that online play was still free and Plus was just a nice perk. With the PS4, PlayStation Plus is a lot more like Xbox Live and Sony apparently needs to get the word out.
Sony has put together a TV ad for PlayStation Plus - the first of its kind - to advertise the fact that you need PlayStation Plus on the PS4 to games online. While Sony did announce this at E3 2013, it stands to reason that there are many potential PS4 buyers who are unaware that online play on the PS4 has moved to the subscription service. It's better to alert them now that they'll have to shell out $50 a year to play online instead of letting them find out the hard way.
As for the actual ad itself, it's another live-action ad that transplants the game world into the real one. There are call outs to Killzone: Shadow Fall, The Elder Scrolls Online, Assassin's Creed IV: Black Flag and more. The focus here is playing with your friends, but Sony does manage to squeeze a small bit about PlayStation Plus' most appealing feature - the free games.
If you still just have a PS3 and/or PS Vita, online play is still free. PlayStation Plus is just a nice service to have. For PS4, Plus is a requirement, but you still get the free games every month, like Outlast.
Image via PlayStation/YouTube