Aviation Terminology

ADS-B: See the ADS-B article in our wiki
ATIS: Automatic Terminal Information Service - A pre-recorded or synthesized recording of weather and other information for an airport, provided by radio and/or telephone.
ASOS: Automated Surface Observing System - A suite of weather instrumentation providing current weather conditions by radio and/or telephone. An ASOS is cooperatively operated by the FAA, NWS, and DoD. An ASOS is not necessarily located at an airport.
AWOS: Automated Weather Observing System - A suite of weather instrumentation providing current weather conditions by radio and/or telephone. Unlike an ASOS, an AWOS is operated exclusively by the FAA.
CTAF: Common Traffic Advisory Frequency - A frequency used for communications among pilots at a particular airport. Pilots, at uncontrolled fields or those with a tower which is closed, will self-announce their intentions to land or take off and communicate between themselves cooperatively on this frequency. Pilot-controlled runway lighting is often controlled on this frequency, using a certain number of microphone clicks to operate the lights.
GCO: Ground Communications Outlet - Allows a pilot to contact a Flight Service Station via radio through a telephone patch. The patch is initiated to a pre-programmed telephone number by clicking the microphone several times. All GCOs operate on 121.725 MHz and are to be used only by aircraft on the ground, not airborne.