Specifically, it compensates for pan and tilt (angular movement, equivalent to yaw and pitch) of a camera or other imaging device. It is used in image-stabilized binoculars, still and video cameras, and astronomical telescopes.
With still cameras, camera shake is particularly problematic at slow shutter speeds or with long focal length (telephoto) lenses.
With video cameras, camera shake causes visible frame-to-frame jitter in the recorded video. In astronomy, the problem of lens-shake is added to by variations in the atmosphere over time, which cause the apparent positions of objects to change. - Wikipedia
