I am always going into the help section of Lightroom while I learn what everything is doing. It's a pain so I am going to copy some down here.
Saturation
- Clarity
- Adds depth to an image by increasing local contrast. When using this setting, it is best to zoom in to 100% or greater. To maximize the effect, increase the setting until you see halos near the edge details of the image, and then reduce the setting slightly.
- 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 skintones from becoming over saturated.
- Saturation
- Adjusts the saturation of all image colors equally from –100 (monochrome) to +100 (double the saturation).
Tone
- Exposure
- Sets the overall image brightness, with a greater effect in the high values. Adjust the slider until the photo looks good and the whites are at the right level. Use Recovery to bring highlight values down.Exposure values are in increments equivalent to f‑stops. An adjustment of +1.00 is similar to increasing the aperture 1 stop. Similarly, an adjustment of –1.00 is similar to reducing the aperture 1 stop.
- Recovery
- Reduces the tones of extreme highlights and attempts to recover highlight detail lost because of camera overexposure. Lightroom can recover detail in raw image files if one or two channels are clipped.
- Fill Light
- Lightens shadow to reveal more detail while maintaining blacks. Take care not to over apply the setting and reveal image noise.
- Blacks
- Specifies which image values map to black. Moving the slider to the right increases the areas that become black, sometimes creating the impression of increased image contrast. The greatest effect is in the shadows, with much less change in the midtones and highlights.
- Brightness
- Adjusts image brightness, mainly affecting midtones. Set the overall tonal scale by setting Exposure, Recovery, and Blacks. Then set the overall image brightness. Large brightness adjustments can affect shadow or highlight clipping, so you may want to readjust the Exposure, Recovery or Blacks slider after adjusting brightness.
- Contrast
- Increases or decreases image contrast, mainly affecting midtones. When you increase contrast, the middle-to-dark image areas become darker, and the middle-to-light image areas become lighter. The image tones are inversely affected as you decrease contrast.
Sharpening
- Amount
- Adjusts edge definition. Increase the Amount value to increase sharpening. A value of zero (0) turns off sharpening. In general, set Amount to a lower value for cleaner images. The adjustment locates pixels that differ from surrounding pixels based on the threshold you specify and increases the pixels’ contrast by the amount you specify.
- Radius
- Adjusts the size of the details that sharpening is applied to. Photos with very fine details may need a lower radius setting. Photos with larger details may be able to use a larger radius. Using too large a radius generally results in unnatural-looking results.
- Detail
- Adjusts how much high-frequency information is sharpened in the image and how much the sharpening process emphasizes edges. Lower settings primarily sharpen edges to remove blurring. Higher values are useful for making the textures in the image more pronounced.
- Masking
- Controls an edge mask. With a setting of zero (0), everything in the image receives the same amount of sharpening. With a setting of 100, sharpening is mostly restricted to those areas near the strongest edges.
