A superconductor works the way it does because of the formation of electrons. Normally, electrons move one at a time through the conductor while having their energy run down from electrical resistance. When an electron moves through two positive ions, the ions are attracted towards the electron and so move closer to each other. A positive charge is formed from the two ions who then attract an electron. The original is effectively a pair as it has another electron trailing it. This is called a Cooper Pair. All the electrons in the superconductor will eventually combine into these Cooper Pairs, which has the net result of no electron being able to slow down as it is locked into another. All the electrons in the superconducting material will be able to move across it smoothly without losing any energy in the process.
Just how much energy is saved in a superconductor? Half of the electricity in North America could be sent to Japan on a superconducting wire as thick as a basketball. | 
