Notice that the histogram is simply linearly shifted to the right. Everything got lighter, every tone was affected the same by the Brightness control. The black end has become midrange gray. There was no intelligence in the process, every value was simply moved to the right by adding a constant value to every tone. This is not the best control.
Contrast emphasizes the differences between light and dark.
Blacks are blacker, Whites are whiter. As in the Brightness control above, the change is not dependent on the image data, the overall range was just stretched. The histogram shows at a glance the situation and the possibilities. Love and honor thy histogram. New black pixels.