Simply put, the brain retains an image for a quarter second after that image has been removed from the retina. Fix your gaze upon an object for a moment and close your eyes suddenly. Notice that the image will remain briefly before fading. This natural phenomenon is the basis for much of the entertainment industry. Without it, motion pictures and television as we know them would not exist.
Television approaches the process from a different perspective.
Basically, an electron beam scans a scene focused on a photosensitive electron tube. The beam scans across the face of the screen until an entire line is scanned. The beam then skips a line and begins its scan again. This continues every other odd numbered line until the bottom of the screen is reached and 262 lines have been scanned. The beam then returns to the top and begins to scan the even numbered 262 lines.