Trimming a pot is about removing excess clay to refine its shape when it is leather-hard. This is done by centering the pot on the wheel or by hand-holding it. Since the rim is usually well finished during throwing itself, the base of the pot is worked upon and a foot-ring is marked for the pot to get a distinct contour.
Trimmings (dry shavings) are wetted and recycled to prepare fresh clay! Engraving, embossing, creating textures on the pot is called fluting. It also includes attaching handles or decorating it with hand-built clay pieces. This is done after trimming, while the pot is leather-hard (neither too wet, nor too dry), after which it is not possible to do much because they are too dry and liable to break.
