We can find two kinds of monitors:CRT and LCD.
CRT:means cathode ray tube like the computers that we have in my school library.
LCD:stands for liquid crystal display like labtobs and flat monitors.
The difference between them are alot but CRT is more expensive and powerful and you can use it for a long time and it wont be slow or tired but LCD is cheaper but with a nice design than CRT.
All monitors are made up of green, blue and red colours.
Also when we want to see how many inches are the monitors, it should be from one corner to another corner 19 inches. But the CRT monitors with plastic , from beginning of the corner to another is 19 inches but without plastic and only the glass should be 17 inches long.