For more precise control over the exposure, you can choose the More option in the Exposure dialog, which lets you manually adjust contrast or brightness using a sliding scale.
Brightness adjusts the overall level of light in the image.
The original overexposed image
Image corrected by reducing brightness
Contrast is the relative difference between the dark and light colors in the image. When you increase the contrast, the dark colors become darker and the light colors become lighter.
Adjusting contrast
Original image
Image after increasing contrast