Open a shot in RAW, and click on the Highlight Clipping Warning at top right of the page, above the histogram - it's a small triangle. If any part of the photo is blown, you'll see a red rash (push the Exposure slider to the right and some will appear if there isn't any already there). Now move the Recovery slider, and the red will reduce. This is pulling back the blown bits of the image. Obviously there is a limit as to how much you can do with this, but it's a useful tool.
The left side triangle, logically enough, highlights under-exposed bits of a shot, highlighting the dark areas in blue. You can boost the Exposure or use Fill Light to reduce this.