What is an Unshielded Twisted Pair Cable?
This is technically just what it says that it is. It is a pair of twisted wires that run through a cable. The significance of the pair is that the same signal uses both wires to create a more stable signal. Each wire is insulated and then twisted into an unshielded cable. There do exist shielded twisted cable pairs and some installations may merit the shielding which acts as a ground though typically it is only installed in business locations.
Some unshielded twisted pair cables may contain more than one pair. Examples of uses of this sort of cable are multiple telephone lines that run through the same cable. Some network cabling may take advantage of this possibility as well.
Unshielded Twisted Pair Connector
At each end of a cable you will need a connector of some sort to allow the correct wires to contact the correct wires in the components that you are connecting. The RJ-45 connector is the standard connector for unshielded twisted pair cable. The RJ stands for registered jack and the connector is designed so that it can only be inserted one way.
It is generally a plastic end with a clip that resembles a wider version of standard telephone wire. It is important to keep in mind that there are different varieties of twisted pair cables and that the telephone extensions that you get in grocery stores are a different sort of cable.