Original: Some of the names for the various weights of yarn from finest to thickest are called lace, fingering, sport, double-knit (or DK), worsted, aran (or heavy worsted), bulky, and super-bulky.
Simplified: Yarns come in many thicknesses or weights from fine to thick: lace, fingering, sock, sport, double-knit (or DK), worsted, aran, bulky, and super-bulky.