After performing base grinds, machined edge sharpening or hand side edge sharpening with a file, a hanging burr can be formed which may feel like a razor sharp corner. This can create hooking of the edge and unexpected edge action. Removing the burr is necessary and and easy final edge tuning step.
By placing a hard stone on the base edge, and run along it, the burr can be knocked off and the edge corner polished smooth. A rubber abrasive (dressing, grinding rubber or gummi stone can follow to smooth the sharp corner further. This is shown at 6:10 on this video.