Raise color intensity where a photo needs it instead of everywhere at once. Vibrance measures how saturated each pixel already is and pushes the muted ones hardest, which is why a sky can gain depth while a face stays natural.
Vibrance vs saturation
A plain saturation slider multiplies the distance between each channel and gray. That treatment is uniform: a dull olive and a pure red both get the same relative push, and the red clips first. Vibrance inverts the priority. A pixel at 20% saturation receives most of the boost, a pixel at 80% receives almost none, and fully saturated colors are left alone.
The practical result: landscapes and product shots take a stronger setting before they start looking processed. Values between +20 and +50 cover most photos. If you need a uniform push instead, the saturation adjustment tool is the better fit.
Skin protection
Skin sits in a narrow orange band where red exceeds green and green exceeds blue. The protection control finds that band and scales the vibrance change down inside it. At the default of 60% a portrait can take a strong vibrance value without the subject turning sunburnt. Drop it to 0% for images with no people, or when an orange subject such as autumn foliage should receive the full boost.
Negative values
Negative vibrance mutes the image gently. Because the reduction is weighted the same way, it pulls color out of quieter areas first and leaves the strongest accents recognizable, which reads closer to a faded film look than a gray wash.
Mix
Mix blends the adjusted image back into the original. It is the fastest way to retreat when a setting is correct in direction but too strong: leave the sliders where they are and lower mix until the photo settles.