In general "bracketing" means taking a series of shots near the settings you or your camera has chosen.
There are two kinds. Exposure bracketing attempts to achieve the perfect exposure (sort of a shotgun approach) while the goal of Depth of Field (DoF) bracketing is to achieve the perfect composition.
Exposure bracketing involves the photographer or camera takeing an exposure at the suggested speed, aperture and ISO, then one or more exposures while varying either the speed, aperture or ISO setting. Usually, there is one or two over and one or two under the suggested by a full, half or third stop.
DoF bracketing can be considered part of the composition and artistic interpretation, something better left to the photographer rather than the camera. First, one exposure is taken at the suggested speed, aperture and ISO settings, and then one or more exposures are taken while varying the aperture and a complimentary change in speed or ISO setting that compensates for the change in aperture. So, two settings are changed not just one.
Canon cameras once had a function also called DoF bracketing that allowed the photographer to focus to select the nearest and furthest points they wanted in focus. This locked in that focus range by setting the aperture even while modifying the other two settings. I haven't owned a Canon or worked at a camera shop since Moses' time so I'm not sure if Canon still uses that terminology.