PIPED BOX covers have a row of piping top and bottom, like this - but usually in the same colour as the body of the cushion, our contrast is just for clarity.
PLAIN BOX covers have seams as shown (in black), but no piping.
ECONOMY BOX covers are super simple with a single seam at the sides and pleats at the corners to accommodate the thickness of the filling. Large ones of these may have to have a seam across the front as well.
PIPED PILLOWS are exactly as their name implies, simply two rectangles sewn together like a pillow case or scatter cushion cover, with piped seams.
PLAIN PILLOW - as above, but no piping.
Please note - you can’t put a box shaped cushion in a pillow edged cover, so pillow covers are not suitable for traditional sofa or arm chair seat or back cushions. Go for “economy boxes” for these if budget is a major priority!