Display control on the monitor allows you to make the monitor brighter or darker, usually represented by a sun icon. The image is an example of what monitor control icons look like, including the icon for brightness control.
What is the brightness icon?
The brightness icon is often represented as a sun (circle with several lines around the circle) or a light bulb. When dealing with buttons or options that increase and decrease the brightness, the sun rays (lines) may be bigger to represent increasing and smaller to represent decreasing the brightness. The sun may also have a plus or minus symbol to represent increasing and decreasing the brightness.