What is Rolling shutter in video?

I am checking the information for producing movie with DSLR. Although I am not consider to buy one, I will encourage my friends to buy it and lend it to me~!!!! I think it have some value in some kind of shooting situation. Before that, I must do some studying. Pro-videographer often concern the rolling shutter issue in some forum. Barry Green explain it clearly.

SENSOR ARTIFACTS AND CMOS ROLLING SHUTTERby Barry Green

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