Aspect Ratio is the ratio of a picture's width to its height.

NTSC television uses a 4:3 aspect ratio.

HDTV and SDTV feature a 16:9 aspect ratio.

Movie theaters typically use an aspect ration of 1.85:1 or 2.35:1.

Converting a movie to television requires either pan and scan or letterboxing.

Pan and scan is a process where technicians remove portions of the left or right side of the video to convert the aspect ratio.

Letterboxing is displaying the full picture in the center of the screen, with black bars above and below it.Aspect Ratio