The DJI Zenmuse H3-2D gimbal stabilzes a GoPro Hero 3+ camera in two dimensions. Stabilization is what keeps the camera pointed at the same place despite motion of the aircraft. A gimbal basically counteracts changes in the aircraft's attitude to keep the camera as steady as possible.
Here is the standard image that is used to describe the axis of motion of an aircraft.
Yaw, which can be thought of as compass heading, is easy to see on a compass. If you have an iPhone you can play with your compass app to get a really good idea of what pitch and roll mean.
Check out a video here:
Here are a couple of scenarios:
A) If the aircraft suddenly pitches down due to a headwind, the gimbal will pitch (tilt) up a bit to compensate. Great.
B) If the aircraft yaws (rotates) a bit, it will counteract this motion by panning a little to negate this motion. Great!
C) If there is a pitch and a yaw that occur at the same time, the 2D gimbal will pan and tilt the gimbal to counteract the motion, but due to the compound nature of the angles, a bit of roll will be introduced. Booo!
The H3-2D gimbal didn't handle this situation very well, but the new one does. The Zenmuse H3-3D gimbal will keep the angle of view steady throughout all sorts of maneuvers. There is a limit to how far it can keep it steady, but it keeps up great for everything we have thrown at it!
I hope that helps.