A television contains a cathode ray rube (CRT) with two basic parts. The electron gun in back shoots a beam that lights up pixels, which are organized in scan lines, on the screen in front.
One interlaced video frame consists of two fields—the first created by scanning odd numbered lines; the second created by scanning even numbered lines. Video is displayed at 30 fps, or 60 fields per second.
A progressive scanned frame of video is scanned in a single pass, with each line scanned in order. Progressive scanned video can be displayed at 24, 30, or 60 fps.