Twill is a basic weaving technique that produces diagonal stripes on the fabric’s surface. The stripes are created because the warp threads pass over or under at least two weft threads, while the point of attachment shifts laterally with each weft. A twill where the warp and weft threads go over and under two threads is called a 2 x 2 twill.
Denim is an example of chenille or twill. The warp threads are usually coloured, and the weft is white, giving the fabric its characteristic white tones. Denim is often made in 3 x 1 twill, where the warp threads run over three weft threads and under one, giving a durable fabric.
Sources
Fabric Link – Textile Dictionary 
Masterclass – What Is Twill Fabric? Definition and Characteristics of the Popular Twill Weave
December 2023, TÄNKOM | Revised March 2024 RETHINK
