A screen or display belongs to the standard computer equipment. It is a so-called Standard output device.
All Windows programs have the possibility to draw objects on the monitor screen.
The screen is made up of thousands of dots, called pixels. They are arranged on a grid whose horizontal and vertical amount of pixels (tiny dots) is fixed. The number of pixels defines the graphical resolution - the most important quality factor for a screen.
Some typical resolutions are (width by height in pixels):
Each pixel on the screen can have its own color. The number of colors you can use varies between 256 (minimum amount) and a very high number which lets the objects appear in their true natural colors.
Depending on the grouping of these colored dots, different objects are displayed. This is what makes verbalization of the information on the screen extremely difficult for the screen reader software.