When Apple released the iPhone 7 Plus last year they promised that more features would be coming down the line. That included a major portrait mode which used the dual lenses on the rear faces camera to take photos with maximum impact.
Here's how they're selling the feature in a new video.
Basically all the phone is doing is snapping two pictures - one each with the dual lenses on the back. One focusses on the background, the other on the subject and then the two are merged, with everything but the subject being blurred out. The result is a fabricated high depth of field shot, similiar to what you might get using a DSLR with a portrait lens.
It's not a new feature, other smartphone makers have been creating similar effects for years, but because it's coming from Apple its being painted as revolutionary. The results look great in the video - obviously - but we'll have to wait and see how it works in the real world.