The Motion > Stabilization effects
Imagine that the video sequence you just have loaded is slightly shaking. It's a common situation when you're using cameras fixed to a mobile support, for examples hand-held video footages, video sequences shot on a boat, etc...
Source ImageSlight shakes
It is possible to avoid these undesired shakes by adjusting each images as the sequence goes along. If you proceed image after image it can be quickly tiresome.
Fortunately, the Motion > Stabilization 1 point and 2 points effects will take it in charge.