system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is there a difference between when a screen is off and when it's showing a completely black screen? Logically you'd think they'd be the same, but obviously a black screen with the monitor on is slightly brighter.
gpt
A typical LCD screen has a backlight. This is why the screen seems slighly illuminated, even though the actual pixels are black. Pixels just define the color and the backlight makes them visible. If your backlight was broken, you could hardly see anything on the screen.

The great difference comes with LED screen. In LED screens each pixel is an individual LED - a small lamp - which defines the color, but also the brightness and there is no separate backlight. This makes black appear much darker.