In multi pair cable sets, for example a Cat. 5 cable, the wires of each pair are twisted to prevent mutual induction into the other cable pairs. The tighter the twist, the less amount of induction into the other cable pairs.
The ground wires are twisted together and then connected to the GFCI ground. The black and white wires may also be twisted together and then using a jumper wire connected to the GFCI. Hard to say without seeing exactly how it is wired.
2 wires
Ethernet cable. 8 wires in 4 pairs. The wires are twisted around each other and covered with a plastic tube to help prevent interference. The wires are also each in plastic.
There are 4 pairs, 8 wires in total.
The same reason telephone transmission wire pairs are twisted: to improve transmission by reducing noise pickup. See related question on twisted pairs.
twisted pair wire is limited in distance, bandwidth, and data rate.
Twisted pairs
twisted-pair
No. Coaxial cable is a single wire that has a thick coating around it. A common use of coaxial cable is for cable television. This is the cable that goes from the jack on the wall into your cable box. Twisted pair contains multiple cables which are split into pairs and twisted together. CAT5/CAT5e/CAT6 cable are all examples of twisted pair. There are a total of 8 wires inside. Every two wires are twisted together to form a pair. The purpose of the cables being twisted together is to reduce electrical interference between the wires.
carry electrical signals...
So that any external EM noise is evenly distributed across all the wires, rather than only concentrated on the wires closest to the source of the noise. It helps cancel out crosstalk.