What is the difference between Ruffle and Pleat?

The difference between ruffle and pleat is that "ruffle" is any gathered or curled strip of fabric added as trim or decoration and "pleat" is a fold in the fabric of a garment, usually a skirt, as a part of the design of the garment, with the purpose of adding controlled fullness and freedom of movement, or taking up excess fabric. There are many types of pleats, differing in their construction and appearance.