Cabling - Why "Twisted Pair" ?

Each network cable contains four pairs of wire, each pair twisted at a regular rate. Better grades of cable deliberately apply different amounts of twist to each pair. 10-Base-T and 100-Base-T lines use two pairs, one to transmit and one to receive data, copper Gigabit uses all four pairs. The twists provide a consistent impedance along the length of the cable, reduce the crosstalk between pairs and tend to make induced noise cancel out.