[Andrea Chung]

excerpt from Wikipedia that explains it re: rolling shutters:

As opposed to a global shutter, where the whole of the sensor is presented with light at once, resulting in the whole of the frame being captured simultaneously, with a rolling shutter, the image is captured sequentially in thin rows from top to bottom, one after the other, over the course of a single frame.

Rolling shutters have the potential to frustrate videographers by creating rolling shutter “artifacts” due to the possibility of the camera moving during the time when the top and bottom of a single frame are captured. This can result in issues such as “skew”, “partial exposure” and what is colloquially known as the “Jellocam” phenomenon.

& this article:

https://dvxuser.com/jason/CMOS-CCD/