What does Natural Fibres mean?
Any raw material with a hairlike composition that is sourced from a vegetable animal, or mineral source and can be spun into yarn; and eventually, woven cloth.
Heddels explains Natural Fibres
There are two main types of natural fibers: those derived from plants, and those derived from animals. Plant-based or cellulosic fibers are composed of cellulose, a carbohydrate similar to starch. They can create a wide variety of fabrics, from fine muslins and organzas to heavy denims and canvas. Examples of plant-based fibers include cotton, ramie, sisal, and hemp.
On the other hand, animal-based fibers are composed of protein keratin, found in hair fibers. These fibers are spun into yarn, then knitted, woven, or felted into many different fabrics. Examples of animal-based fibers include silk, wool, alpaca, cashmere, and mohair.
A snapshot of cotton, a natural fibre: