Long ago, wool yarns were described as "worsted", or "woolen", or something in-between. A true "worsted" yarn is spun from combed fiber, which is dense and fairly smooth. A true "woolen" yarn, on the other hand, is open, airy, fuzzy, and warm. Its fibers comfortably tangle and spiral down the length of the yarn. The descriptive words not only apply to the yarns, but also to the techniques used to spin them. Worsted spinning is done with a short draw -- a short drafting movement. Woolen spinning uses a long draw.
The woolen long draw requires carded fibers rolled into shapes called "rolags" to obtain its characteristic tangly spiral. Without rolags, the long-draw drafting technique suffers and the yarn is not a true woolen, but rather... something else.
Here is an introduction to spinning true woollen using the long-draw drafting technique. Enjoy!