Unshielded Twisted Pair (UTP)
Unshielded is the most common type you'll find in use. It does not have a metallic layer of shielding within the cable. Shielded cable is normally only required in severe electromagnetic interference environments. Unshielded cable is fine for home use.
All networking cable is twisted pair cable (each of the 4 pairs are twisted together). Having the pairs twisted helps reduce/eliminate noise on the network signal.