Exposure bracketing is a simple technique professional photographers use to ensure they properly expose their pictures, especially in challenging lighting situations.
In short, bracketing is taking the same photo more than once using different settings for different exposures. Why would you do this? Say you’re photographing a mountain landscape. The grass would require one setting to be properly exposed, the mountains would require another and the sky yet another. But you can only choose one setting for one photo. Shoot! Now what? Try bracketing!