Ruffles and frills are two different words that are used in a different context. Ruffles are used to refer to so many things; it refers to sewing, a strip of closely pleated cloth or fabric used for decoration or trim; it also refers to the ruff of a bird.
It refers to fray or ruckus. It also means annoyance or vexation. In the fashion world, it refers to a fabric, lace, or ribbon which has been tightly gathered at one end. Also, in the fashion world, it is considered to be wider than frills. The cut done on ruffles are different.
Frills refer to a pleated, gathered projection, fabric, ribbon, lace. It also refers to a ruff of hair on the neck of a bed. Luxury, wrinkling that takes at the edges of a photographic film. In sewing, it refers to smaller pleats which are made with either fabric lace and sewn on the edges of skirts or dresses.