Fibers are elongated strands of material that can be twisted together to form thread or yarn. They can come from animals -- such as wool fiber from sheep, plants -- such as cotton fiber from the cotton plant, or can be manufactured -- such as nylon, if you really want to know, "a flexible thermoplastic polyamide."
Fibers from different sources have different characteristics, and will result in different finished yarns. Some important characteristics of include the width and length of the fiber; crimp, the number of "bends" in a given length of fiber; and luster, the sheen of the fiber surface due to light reflection.
Both animal and vegetable fibers can be considered renewable resources. Every year, the sheep or other animal is kind enough to produce another fleece The cotton plant produces another round of bolls. The bamboo plant continuously grows, allowing us to harvest it and obtain its fibers. Spinning can be truly environmentally friendly, as long as attention is paid to good practices