Cathode ray tube (CRT) is a vacuum tube containing one or more electron guns. They worked on the principal that when an electron hits a phosphor; which the screen is coated in, lights up for a short period of time.
The electrons are emitted by a small metal element at the back of the display that is heated, they are then accelerated by a potential difference across the anode(A metal plate with a hole through the middle) and the cathode(The top part of the element)
The electrons are directed to a particular pixel on the screen via electro-magnets, this process needs to happen thousands of times per second as it need to hit every individual pixel between 50 and 60 times per second (depending on where the display is from Europe: 50 USA: 60) otherwise the image will fade.
Theresa Knott Cathode ray Tube Image source
