Docking refers to attaching a control to either an edge (top, right, bottom, or left) or the client area of the parent control. On the other hand, anchoring is a process in which you need to specify the distance that each edge of your control maintains from the edges of the parent control.
Anchoring treats the component as having the absolute size and adjusts its location relative to the parent form. Docking treats the component location as absolute and disregards the component size. So if a status bar must always be at the bottom no matter what, use docking. If a button should be on the top right, but change its position with the form being resized, use anchoring.