Taking the same shot at a series of different exposures with the intention of choosing the best one later or merging them together to create an HDR image. Most cameras offer an auto exposure bracketing option. You choose the bracketing interval (the difference between the exposures, typically 1EV) and the number of frames (usually 3, sometimes 5 or even 7). Some cameras offer other types of bracketing, e.g. white balance bracketing or even focus bracketing.