RTF (Ready to fly): A RTF plane includes the plane with the radio, receiver, battery, charger, motor, servos, retracts (if it has) and ESC already in place.
PNP (Plug and Play) - A PNP foam plane includes the plane with the motor, servos, retracts (if it has) and ESC already in place. Battery and charger are not included. Radio and receiver are not included.
KIT: A KIT plane is an airframe only. It does not include any motor, ESC, or servos (though usually includes servoless retracts on planes with retracts).