Narita International Airport, in Tokyo, Japan.

What is the difference between NRT and RJAA?

NRT is the IATA code, used commercially — tickets, timetables, luggage tags. RJAA is the ICAO code, used operationally by pilots and air traffic control, and assigned geographically by region.

Is NRT the same as HND?

No. HND is haneda, far closer to Tokyo and increasingly the one long-haul carriers use.

What airport is NRT?

NRT is

Narita International Airport

Tokyo, Japan

Why the code is NRT

NaRiTa, the city it sits in, 60 km from Tokyo.

The airport authority or a contemporaneous record states this directly.

The airport

IATA code: NRT
ICAO code: RJAA
Airport: Narita International Airport
City: Tokyo, Japan
Opened: 1978
Code origin: Documented

Narita was built over the objections of the farmers whose land was expropriated, and the resulting protests delayed it by years and left the airport ringed with security fencing and watchtowers that are still there. One farmhouse held out inside the airport perimeter for decades.

Codes people book by mistake

Code	What it actually is
HND	Haneda, far closer to Tokyo and increasingly the one long-haul carriers use.

The other code, RJAA

Every airport has two codes. The three-letter IATA code, NRT, is the one on your boarding pass and your luggage tag, and it is assigned for commercial use. The four-letter ICAO code, RJAA, is the one pilots and controllers use, and it is assigned geographically: the first letter or two identify the region, so every airport in the same part of the world shares a prefix. That is why RJAA looks nothing like NRT.

Common questions

What airport is NRT?: Narita International Airport, in Tokyo, Japan.
Why is Tokyo's airport called NRT?: NaRiTa, the city it sits in, 60 km from Tokyo.
What is the difference between NRT and RJAA?: NRT is the IATA code, used commercially — tickets, timetables, luggage tags. RJAA is the ICAO code, used operationally by pilots and air traffic control, and assigned geographically by region.
Is NRT the same as HND?: No. HND is haneda, far closer to Tokyo and increasingly the one long-haul carriers use.

Japan Capital, area, population and currency
The flag of Japan Colours, symbols and lookalikes
Airport codes in Japan 3 here
What airport is HND? Tokyo Haneda Airport
What airport is HND? Tokyo Haneda Airport, Tokyo
What airport is KIX? Kansai International Airport, Osaka

Sources

OurAirports — OurAirports (Public domain)

How these figures are compiled and checked