An electron gun in a CRT display fires a stream of electrons at the phosphor-coated display screen. Electromagnets in the yoke deflect the stream horizontally and vertically. This beam scans left to right, one line at a time, from top to bottom. This cycling refreshes the display many times each second. If a pixel is meant to be turned on, the electron beam "hits" it as it scans by, and the phosphor glows at that point. The control of the guns and deflectors is handled by the computer's video adapter.
