Every color adjustment tool in Photoshop — Curves, Color Balance, Selective Color — operates on the same underlying logic: the RGB color model. Understanding how red, green, and blue light combine, and how tonal values are distributed across highlights, midtones, and shadows, gives you the foundation to use any of these tools
Read the full article here: Understanding RGB, Curves, and Color Adjustment Tools in Photoshop Photoshop Roadmap