Original: An IATA airport code, also known an IATA location identifier, IATA station code or simply a location identifier, is a three-letter code designating many airports around the world, defined by the International Air Transport Association (IATA).
Simplified: An IATA airport code, is a three-letter code that can be used to identify airports. This removes the need to write the name of the airport in full every time it is needed, instead an IATA code can be used.