Deinterlacing is the process of converting interlaced video into a non-interlaced or progressive form. Interlaced video signals are commonly found in analog television, VHS, Laserdisc, digital television (HDTV) when in the 1080i format, some DVD titles, and a smaller number of Blu-ray discs.
When someone watches interlaced video on a progressive monitor with poor deinterlacing, they can see "combing" in movement between two fields of one frame.
Interlaced video is a technique for doubling the perceived frame rate of a video display without consuming extra bandwidth. The interlaced signal contains two fields of a video frame captured consecutively. This enhances motion perception to the viewer, and reduces flicker by taking advantage of the phi phenomenon.
When someone watches interlaced video on a progressive monitor with poor (or no) deinterlacing, they can see "combing" in movement between two fields of one frame.