From the SpaceX Channel:
“On August 13th, the Falcon 9 test rig (code name Grasshopper) completed a divert test, flying to a 250m altitude with a 100m lateral maneuver before returning to the center of the pad. The test demonstrated the vehicle’s ability to perform more aggressive steering maneuvers than have been attempted in previous flights.
Grasshopper is taller than a ten story building, which makes the control problem particularly challenging. Diverts like this are an important part of the trajectory in order to land the rocket precisely back at the launch site after reentering from space at hypersonic velocity.”