Special Flood Hazard Area (SFHA)
The Special Flood Hazard Area is the area FEMA's flood insurance rate maps show as the 100-year floodplain, meaning land with a 1% chance of flooding in any given year.
New Jersey example
The Flood Risk Notice New Jersey landlords use for rentals, such as an apartment in Lambertville, asks whether the property is wholly or partly in the Special Flood Hazard Area on FEMA's current maps, and whether that is based on an effective or a preliminary map. It also asks about the Moderate Risk Flood Hazard Area, the 500-year floodplain with a 0.2% annual chance.
Official source
Flood Risk Notice (NJ Department of Community Affairs model notice under N.J.S.A. 46:8-50)
This is a plain-English summary. Rules and dollar amounts change, so check the official source or a professional before you file or sign anything.