They're called LEGO Fusion, and their big new feature is the ability to digitise whatever your structures—to put them on your tablet or phone, basically, where you can then play around with them in various ways.
To facilitate this, each Fusion set includes (apart from a set of bricks, of course) a Fusion capture plate. The process looks like this: you build an up to 16 by 16, 2D wall on the capture plate, you take a photo of the wall with your phone's or tablet's camera, and the LEGO Fusion app then interprets the photo, creating a virtual 3D version of whatever you built.
Actual gameplay changes depending which set you get. For example, Town Master has you build and manage a town, where the task is to keep your citizens happy. In Create & Race, you build a racecar which you can then use to drive around on an in-game racetrack. Basically, you're going back and forth between the app and the capture plate as you play.
Four LEGO Fusion sets—Town Master, Battle Towers, Create & Race, and Resort Designer—have been announced so far for a 2014 summer release.