What exactly does Tone Curve do in Lightroom?

Question

In simple terms, what does Tone Curve in LR actually do?. I can see the results of changing Tone Curve by playing around with it, but I don't really understand scientifically what it actually does. I read a few documents on it, including one from Adobe, but I just got lost.

Answer 1

When taking a picture, your camera registers light according to its value on a grey scale or value scale. Your camera meter tries to match the correct tone of grey when reading light, which is why photographers sometimes use a grey card to do a light reading. In digital color film, tones are created with a combination of red, green, and blue (RGB). So, when you mess with your tone curves, look at your histogram to see how the changes affect the heights of the peaks for the true colors and their combinations. Your adjustments to the tone curve dictate what colors (tonal range of colors) on your photograph will appear lighter or darker.