Progressive Scan: Each individual frame is produced by displaying every scanline (horizontal strips of picture data) top to bottom, 60 frames every second for NTSC, 50 for PAL.
Interlaced: Each individual frame is produced by interlacing 2 fields together, each field consists of every other scanline and are shown 1 after the other 60 times a second or 30 frames every second for NTSC, 25 for PAL.
Your computer monitor displays video using progressive scan, normal analog TV is interlaced broadcast video.