Lightroom: The Histogram and the Basic SectionPost 15
If you move this slider to the right the whole histogram moves to the right side of the graph, extending the shadows. Moving the other direction extends the highlights. Depending on the direction you choose, the highlights become lighter or the shadows darker.
The Exposure and Contrast sliders are very important in changing the look of your shot. Make these adjustments first.
In the Shadows
In the Black
The Blacks slider controls the tones on the far left. I recommend not removing all of the blacks from the shot because most images work better when they have some areas that have areas of pure black.
Contrast and Clarity sliders should be done FIRST before saturation because increasing the contrast of the shot will boost its saturation.
The Clarity slider gives mid tones more contrast. Pulling the slider to the right will make the image appear sharper and crisper while pulling the slider to the left creates a softer look. The less-is-more idea fits well with this slider.