FL is the written short form of Florida, a state in the south-east of the United States. You see it on envelopes after the city name (Miami, FL), on car plates, on maps, and in weather reports. Both letters are capitals, and there is no full stop. People almost never say “F-L” out loud for the state — they just say Florida. Though actually, FL can mean other things in other jobs and codes; in a US address it is Florida and nothing else. It is a state, not a country.

佛羅里達州（書面縮寫；台灣新聞也常寫「佛州」）