Facebook has an estimated 1.3 billion users (yes, billion with a "b"), but it wants even more. The problem is that many people in the world, including quite a number in the U.S., don't have reliable, fast Internet access.
That's not exactly surprising. A lot of developing countries just don't have the infrastructure in place. And America has the problem of how expensive it is to run Internet cables over huge distances with sparse populations. However, Facebook thinks it has found a way around that little problem.
In word, "drones." And it makes sense. Bouncing a signal off a couple drones costs a lot less than running thousands of miles of cable, or, going the other direction, putting satellites in orbit.
However, Facebook's drone isn't one of the little quadcopters you usually see flying around. It isn't even like one of the military's larger combat drones. No, this is something else entirely.