What is the difference between vibrance, saturation and clarity in Adobe Lightroom and Adobe Photoshop?
This first bit is from the Adobe site.
Vibrance adjusts the saturation so that clipping is minimized as colors approach full saturation, changing the saturation of all lower-saturated colors with less effect on the higher-saturated colors. Vibrance also prevents skin tones from becoming oversaturated. Saturation adjusts the saturation of all image colors equally from ‑100 (monochrome) to +100 (double the saturation).
Now my observation: As a test, I processed an image with the Vibrance slider all the way to the top and Saturation at zero, then the other way around. Vibrance is less extreme and does a balancing act to keep things from getting too saturated as well as keeping skin tones more natural looking.