Let Me Tell You, Boyo...
The Tesla Coil is an air-core transformer with primary and secondary coils tuned to resonate. The primary and secondary coils function as a step-up transformer which converts relatively low current at high frequencies.
The Tesla Coil demonstrates the fundamental principles of high frequency electrical phenomena. It illustrates the principles of the ionization of gases and the behavior of insulators and conductors when in contact with high frequency electrical fields.
As conceived by the inventor Nikola Tesla, the Tesla Coil was developed to transmit electrical power without wires. An antena would be constructed to pull the transmitted electrical energy into the electrical system. The Tesla Coil can be considered a simple radio transmitter, operating within a broad range of high frequencies, which transmits power rather than information.
Yeah, right. Thanks for that. That's really cleared up all that a whole load. (extract courtesy of Channel 7 - well, not much courtesy, I just nicked it off their webpages)
All you need to know is THIS: