Say you have your display, this is made up of millions of lights that on their own just light up in whatever single colour you want, but together they light up to create an image.

Your software takes care of breaking down that image of a cat you want to look at into its corresponding pixels - with a value for colour and brightness.

For example it'll say this area in the cat's eye is black, so it'll request the no light to come out of it. Another area might be a pale red so it'll request red with some middle level of brightness.

Now your firmware takes that requested black for a specific Pixel and it'll physically cut power to switch off all the lights in the required area. For the pale red it'll power that the red ligh ON with hald power, whilst green and blue are OFF.

(things get more complex once you consider back-lightning)