Sliders are Lightroom magic. Before there were sliders, tones and colors were adjusted with tone curves. The big benefit I see with the Tone Curve module is that it helps to explain what the contrast/highlights/lights/darks/shadows sliders are doing under the hood. Therefore, it is worth playing with even if you will use sliders 99% of the time. With curves, you can work with finer control than sliders provide.
For this set of examples, I used a landscape picture with a partially cloudy sky with trees and fields in the middle ground.
Before, and after changing the Tone Curve (more than the Highlight slider can do), emphasizing the detail in the sky.,
To read the whole talk, see this pdf: Understanding Basic Sliders by Looking Under the Hood.pdf