What is Clipping?
Clipping happens when you have areas with no information in your photo. When an area has no information, it is either pure white or pure black. Photographers often refer to these areas as "blown out". Generally, it is undesirable to have large areas of your image with areas that have highlight clipping or shadow clipping.
Clipping Warnings in Lightroom
Lightroom uses added color to warn you of areas that have highlight or shadow clipping. Your screen will show bright red for areas where the highlights are clipped and blue for areas where the shadows are clipped. You can turn these off or on in several different ways. Simply tapping the "J" key will turn both the highlight and shadow clipping off or on.
You can turn them on and off individually by clicking the little arrows on the top left and right of the histogram. The right one will toggle on/off the highlight clipping warning and the left one will toggle on/off the shadow clipping warning.
How to Fix Clipping in your Photo
Just like in any editing program, there are several different options for fixing clipping on images in Lightroom. The most obvious options are to use the Highlights and Shadows sliders in the Basic Panel. Moving the Highlights slider to the left will decrease the Highlights. Moving the Shadows slider to the right will bring back information in the Shadow areas of your photo.
You can also further adjust the highlights and shadows by using the sliders or curve in the Tone Curve Panel.
However, the easiest way to recover the highlight and shadow clipping in your images is to use the presets included in a couple of our sets. The Pretty Presets Workflow Collection has presets for recovering both highlight and shadow areas of your image (Exposure Recover Clipping and Exposure Lighten Shadows). The Clean and Creative Advanced Workflow has a preset for recovering clipping as well called "Recover Clipping".
A little bit of shadow or highlight clipping doesn't bother me too much—especially if it isn't in key areas of your photo. If there are small areas where the highlight or shadow clipping just can't be recovered and it isn't distracting to your photo, don't stress over it too much!
Special Thanks to Allison Wheeler for this wonderful video that also talks about clipping and shows you the different techniques to fix it!