Base flood elevation (BFE) is the height, in feet, that floodwater is expected to reach during a "base flood" (a flood with a 1% chance of happening in any given year). FEMA maps the BFE for flood-prone areas.
BFE matters because how a home sits relative to it affects both flood insurance pricing and local building requirements. A home built above the BFE generally faces lower flood risk and cost than one below it.
Example: if the BFE for a lot is 12 feet and a home's lowest floor sits at 14 feet, it is two feet above the base flood elevation, which typically lowers its flood insurance cost.
Related: flood zone, special flood hazard area, NFIP. See the flood insurance overview.