A monitor can be adjusted for brightness and contrast, and many monitors have additional controls for moving the image left, right, or up and down. A monitor appears somewhat like this illustration of a "Mitsubishi" monitor:
This particular monitor has high resolution capability of 1600 x 1200 pixels.
Ok, so what is a "pixel"? It is the smallest display area on a screen. A single character, or the space it takes to display a single character, can consist of dozens of pixels. These pixels can be colored to display single colors, or a mix of colors to represent true colors. The number of pixels a screen can contain is the "resolution" of a screen.
"Picture quality" depends on resolution, dot pitch, refresh rate and method, and the type of "phosphors" used in the screen if we are speaking of a Cathode Ray Tube. Other types of screens (LCD, LED, Plasma) have some different factors.
We will talk in more detail if you desire.