The process of transferring a movie or other source material to videocassette, DVD, or broadcast so that it fits the 4:3 aspect ratio of the NTSC system, as well as most current TVs. This results in a significant amount of lost picture information, particularly in the width of the image. At the beginning of a movie on videocassette, you'll usually see a disclaimer about the movie having been "...formatted to fit your TV." That means it's been converted to pan-and-scan.
The technique of reframing a picture to conform to a different aspect ration by cropping parts of the picture. Since the frame aspect of a standard TV set is different than that of a movie screen/widescreen HDTV, a significant portion of the picture will be cropped to fit the full TV screen. DVD-Video players can automatically create a 4:3 pan & scan version from a widescreen video by using a horizontal offset encoded within the video.