Normal video, such as from VHS VCRS, Camcorders, and television broadcasts, is displayed on your TV as a result of scanning series of lines on a screen surface in a format called interlaced scan. In this system, lines of video are displayed in an alternate fashion on a television screen. All the odd lines are scanned first, then all the even lines. These are referred to as fields. This process results in an interlaced image. Each frame on your screen is made up of the two interlaced fields of video. Although video frames are displayed every 30th of a second, the viewer, at any given point in time is only seeing half the image. Since the scanning process is so quick, the viewer's brain perceives the video image on the screen as a complete image.
The Difference Between Progressive Scan and Interlaced Scan
Progressive scan differs from interlaced scan in that the image is displayed on a screen by scanning each line (or row of pixels) in a sequential order rather than an alternate order, as is done with interlaced scan. In other words, in progressive scan, the image lines (or pixel rows) are scanned in numerical order (1,2,3) down the screen from top to bottom, instead of in an alternate order (lines or rows 1,3,5, etc... followed by lines or rows 2,4,6). By progressively scanning the image onto a screen every 60th of a second rather than "interlacing" alternate lines every 30th of a second, a smoother, more detailed, image can be produced on the screen that is perfectly suited for viewing fine details, such as text, and is also less susceptible to interlace flicker.
How To Take Advantage Of Progressive Scan
In order to take advantage of a DVD player's progressive scan feature, you must also have a television that has progressive scan display capability. However, since a DVD player's progressive scan feature can be turned off or on, you can still use a progressive scan DVD capable DVD player on a non-progressive scan capable television.
For a more detailed discussion on progressive scan and how it relates to your own DVD viewing, check out my article: Progressive Scan - What You Need To Know.