Ruffles potato chips are distinguished by their ridges, also called a crinkle-cut or wavy surface.
The ridges give each chip its recognizable corrugated shape and help create a sturdier texture than a typical flat chip. They also provide extra surface area, which can help seasoning cling to the chip and makes Ruffles popular with dips. The brand itself has long emphasized the feature with the slogan “Ruffles have RRRidges.”
Ruffles was created by Bernhardt Stahmer, who adopted the trademark on May 11, 1948. The Frito Company acquired the rights to the brand in 1958. Frito later merged with H.W. Lay & Co. in 1961, forming Frito-Lay, which became part of PepsiCo.
“Ridges” is the canonical answer rather than “waves,” because the brand and product descriptions use that term. Ruffles should also not be confused with ordinary chips that merely have an irregular edge: the defining feature is the repeated, raised-and-lowered pattern across the chip’s surface.