Tesla's system of alternating current generators, motors and transformers powers the world's industry, lights our homes and underpins most modern electronics. Edison, though more famous, backed a direct current (DC) system used today primarily in batteries.
DC vexed Edison because he could not find a way to send it long distances [sources: Jonnes; Vujovic]. He also struggled to convert the alternating current produced by his dynamos into direct current. Edison's solution involved "commutators" -- brushes that allowed current to flow in only one direction but created inefficient friction and required frequent replacing [source: Jonnes].
Tesla's generators didn't require such a cumbersome approach. Moreover, his system could "step up" voltages for transmission over long distances, then "step down" voltages at the destination to levels usable in homes and factories.
Take the electric motor pioneered by Belgian engineer Zénobe-Théophile Gramme. Whereas Edison and others tried to tether the device inefficiently to DC, Tesla revolutionized it by adding a second circuit that would "alternate" a current out of phase with the first, creating the prototype for his successful polyphase system.
The transformer, like the generator, was invented by Michael Faraday, but both lay fallow until Tesla unlocked their potential and, by doing so, harnessed electricity to do the work of the modern world [source: Jonnes].