Twisted Pair - Two conductors that wrap around each other to form a pair. UTP - Unshielded Twisted Pair. One or more twisted pairs inside an insulating sheath. UTP generally has an impedance of 100 ohms. Cables are grouped in categories according to various factors.
Levels specify a certain speed rating on the cable.
IBM Cable Types specify a certain kind of cable. Please note that what is shown below is a very abbreviated description. Each Level or Type has specific physical and electrical characteristics and those details can be found in most cable vendors' catalogs. The number of twists per foot is at least two for data grade cable. The higher level cables have better conductors, insulation and more twists per foot.