ARF, PNP, RTF, RTR - What Does It All Mean?

The Product Format and its three letter acronym are a basic designation which tells you two primary things: 1) what amount of assembly is required and 2) what is included with the model. The following table provides a brief summary of each Product Format. More detailed descriptions are listed below the table.

ARF - ARF stands for "Almost Ready to Fly." An ARF is an aircraft that is "mostly" built with the exception of the main control and power system electronics. ARF's require you to purchase primary electronic components separately (motor, servos, ESC, etc). ARFs are for hobbyists who prefer a true build experience and/or prefer to put their own choice of electronics in the aircraft.
Requires: servos, ESC, motor, receiver, battery, charger, and transmitter.

ARF BUNDLE - An ARF Bundle is an ARF model bundled with all the electronics you need to build the aircraft. While the required electronics are included with the airframe, they are not installed in the airframe. These bundles typically include servos, motors, and ESCs. The bundle simplifies your purchase and saves you money compared to purchasing the required electronics separately.
Requires: receiver, battery, charger, and transmitter.

ARF PLUS - Expanding on the standard ARF format above, the ARF Plus model has all electronic components pre-installed, with the exception of the power system (the power system includes motor, EDF unit, and ESC). All other components, from the retracts to the servos to the lights, are factory installed. ARF Plus models are near ready-to-fly aircraft that give pilots the option of experimenting with custom power systems.
Requires: EDF, ESC, motor, receiver, battery, charger, and transmitter.

FTR - FTR or Futaba Transmitter Ready is identical to Bind N' Fly except that it includes a pre-installed Futaba compatible receiver instead of a Spektrum receiver. You must have a Futaba compatible radio in order to bind to a FTR aircraft.
Requires: battery, charger, and Futaba compatible transmitter.

KIT - KIT typically applies to aircraft, boat, and vehicle models that require a more advanced level of assembly. KITs are generally geared towards hobbyists who enjoy the process of building a model as much as they do driving or flying their models.
Requires: servos, ESC, motor, receiver, battery, charger, and transmitter.

PNP - PNP or Plug N' Play products are near ready-to-fly models requiring typically less than 1-2 hours of build time. PNP models include the ESC, motor, and servos all pre-installed from the factory. Many pilots prefer PNP models because it allows them the flexibility to use any brand of receiver in their aircraft.
Requires: receiver, battery, charger, and transmitter.

RTB - RTB or "Ready to Bind" aircraft include the ESC, motor, servos, and a Xwave receiver all pre-installed from the factory. You must have a compatible Xwave radio (sold separately) in order to "bind" to a RTB aircraft. RTB models do require some assembly, typically 1-2 hours of build time.
Requires: battery, charger, and Xwave compatible transmitter.

RTF - RTF stands for "Ready to Fly". Aircraft that are RTF come with everything you need to fly in the box. A transmitter, battery, charger, receiver, and all other required electronics are included and pre-installed from the factory. All you need to do is charge your battery, attach the wings and stabilizers and you're ready for flight. While everything is included and pre-installed, RTF models can require 30 minutes to two hours of assembly.
Requires: Nothing.

RTR - RTR means "Ready to Run" and is used to describe vehicles and boats that are basically ready to run/use out of the box. Some models may require minor assembly, but everything needed will be included in the box including the radio, receiver, battery, charger and all accessories. 
Requires: Nothing.