Plain English Meaning
A staffed FAA service that pilots call or radio for weather, flight plans, and other flight-related help. Not a control tower — they advise and assist, but do not give clearances or separate traffic.
Full Definition
An FAA facility that provides preflight and inflight services to pilots, including weather briefings, flight plan filing and processing, search and rescue initiation, NOTAM information, and assistance to aircraft in distress. AFSS specialists communicate with pilots by telephone on the ground and by radio in flight, and they relay airport advisory information at selected .