With bezel correction, part of the game view is hidden behind the display bezel so that the bezel appears to be part of the game. This produces a more continuous image across the displays and provides a more realistic experience. It is similar to looking through a cockpit window where the window frames block your view.
When you enable bezel correction, a bezel-corrected version of each 3-wide display resolution is added to the list of available resolutions – both within games as well as within the NVIDIA Control Panel. If you do not use bezel correction and wish to remove the extra resolutions to simplify the list, run the Surround wizard and select No at the “Do you want to use bezel correction?” screen.