Piping is a trim or edging formed by sewing a thin strip of folded fabric — typically bias binding — into a narrow tube and attaching it to the edge of a piece of fabric. It can also include cord to give it extra body. Piping is often used to define or reinforce the style lines of a garment.
Pleats are a fold or doubling of fabric that is pressed, ironed or creased into place. (Pleats that are sewn into place are called tucks). There are many varieties, but the side and box pleat are the most common, although they can be accordion, cartridge, circular, curtain, draped, fluted, Fortuny or French. They can be inserte, as well as inverted. Pleats add an even greater fullness to a shape (particularly the skirt). Think Marilyn Monroe over the air vent in ‘The 7 Year Itch’.
Plissé originally referred to fabric that had been woven or gathered into pleats and has also been known as crinkle crêpe. It takes its name from the French word for fold. Today, it is a lightweight fabric with a crinkled, puckered surface, formed in ridges or stripes. Plissé can also describe a chemical finishing technique, where plisse fabrics are used for underwear.