The following description of a Flight Service Station is taken verbatim from the Airman's Information Manual (AIM) of January 6, 1994:

4-3. FLIGHT SERVICE STATIONS

... Flight Service Stations (FSS) are air traffic facilities which provide pilot briefings, en route communications and VFR search and rescue services, assist lost aircraft and aircraft in emergency situations, relay ATC clearances, originate Notices to Airmen, broadcast aviation weather and National Airspace System (NAS) information, receive and process IFR flight plans and monitor NAVAIDS. In addition, at selected locations FSSs provide En Route Flight Advisory Service (Flight Watch), take weather observations, issue airport advisories and advise Customs and Immigration of transborder flights ...