Definitions for "Air Traffic Control"
A computerized system that performs air traffic control tasks; ATC was necessitated by increased air traffic and enabled by the expanding capabilities of computers.
The government employees directing takeoffs, landings, and flight plans for all aircraft.
A catch-all term for all the folks a pilot might be talking to in controlled airspace (or even outside it). ATC is concerned with keeping aircraft operating under IFR separated, helping pilots spot other aircraft and generally advising or controlling aircraft in real time (unlike an FSS).