I always think of it as a general term for a shape of a state, but specifically I would think of Florida.
And yes, the panhandle of Florida is the northwest part of the state from the Flora-Bama bar at Perdido Key to roughly the Apalachicola River (some say it extends all the way to Tallahassee). It includes the Emerald Coast beaches of Pensacola, Gulf Breeze, Navarre, Fort Walton, Panama City, and Destin among others.