Judder / Motion Blur
A scene is acguired by a camera at a given frame rate (eg 24 frames per seconds) using a given shutter speed, namely the time duration when the photons hit the sensor. Usually the shutter speed is 50% of the frame duration (eg 1/48 seconds in our example).
When motion is present in a scene, some blur appears at the edge of moving objects, this is called motion blur. The higher the shutter speed (eg 1/96 seconds) the less motion blur is visible but another artifact appears: judder. It is when the movement looks jerky enough to be uncomfortable to watch.
Again a good trade-off between judder and motion blur is to set the shutter speed at 50%.