Just about all editing applications have the curves dialogue. The basic idea behind the tool is that it presents the user with a way to adjust tonal ranges in the image, set black and white points, lighten or darken the overall image, as well as adjust colour castes and hues. That’s a lot for one tool which is why it is so important.
This tutorial goes into depth describing how the curves control works in Capture One Pro (version 16.3.1), although it's applicable to any curve dialogue in any editing platform. It's a fairly long tutorial so use the chapters below to jump to pertinent sections, particularly as I start with a refresher on the histogram.
Timeline:
00:00 Intro
01:15 How the histogram works
04:34 How the curve control works
07:16 Example of using the curve control in Capture One and overview of the control intself
09:37 Creating Control Points on the curve
10:48 Increasing contrast using the curve tool
12:41 Available curve presets in Capture One
13:53 Using lock points to anchor a curve section
16:00 Using the curve control and the difference between RGB and Luma curves
18:42 Adjusting contrast in a low contrast image using Luma Curve
19:37 Setting black and white points using the curve control
21:44 Conclusion