BingBumpier
Spinning is the craft of twisting loose fibers into a continuous strand of yarn. It is one of the oldest technologies humans have — predating writing, agriculture in some regions, and probably permanent settlement. Spun thread has been recovered from sites dating back at least thirty thousand years.
Raw fiber, whether wool from a sheep, cotton from a boll, flax from a plant stem, or silk from a cocoon, is made up of short individual strands. By themselves they are weak. By twisting them together so that they wind around each other, you create something far stronger — strong enough to weave, knit, or sew with. The twist is what makes the yarn.
That is the entire principle. Everything else — wheels, spindles, factories — is engineering to apply twist faster, more consistently, and with less hand fatigue.
Industrial yarn is cheap and consistent. Handspun yarn is neither, which is exactly its appeal. You control the fiber blend, the twist, the thickness, and the texture. A handspun skein meant for a particular sweater can be optimized for that sweater in ways factory yarn never will be. There is also the meditative aspect — a treadle wheel run at a steady pace is genuinely calming, in a way that crosses cultures and centuries.
A simple drop spindle and a few ounces of wool roving will run you twenty to thirty dollars and is enough to learn the basics. From there, a used Ashford Traveller or Kromski Sonata wheel in good condition runs three to six hundred dollars and will last decades. Most fiber arts guilds will let you try a wheel before buying one. Take them up on it.