Saturation increases the level of all colors in the image.
Vibrance will increase the saturation of the less vibrant colors in the image.
Clarity increases contrast primarily around the edges of objects. This appears to make the image sharper.
Adds depth to an image by increasing local contrast, with greatest effect on the midtones. This setting is like a large-radius unsharp mask. 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.
Adjusts the saturation so that clipping is minimized as colors approach full saturation. This setting changes the saturation of all lower-saturated colors with less effect on the higher-saturated colors. Vibrance also prevents skin tones from becoming oversaturated.
Adjusts the saturation of all image colors equally from -100 (monochrome) to +100 (double the saturation).
Please have a look at the following articles, it should be helpful : http://layersmagazine.com/clarity-vibrance-and-saturation-in-adobe-photoshop-camera-raw.ht ml
thanks a lot for your helpful answer