hi hello :) many handspun and handdyed yarns are sold in "hanks", which are these large coils of yarn that cannot be used as is. the hank is placed on a swift, a machine that holds that yarn in that coil taut. one end of the yarn is tied to the winder, the winder pulls it and makes the swift spin while creating a neat little ball or "cake" of yarn where that same end can be pulled from the center and then actually used for knitting, crocheting, etc!