About the fahrenheit scale
Fahrenheit is a temperature scale used mostly in the USA. It was introduced almost 300 years ago by a German scientist called Daniel Gabrial Fahrenheit.
The symbol for Fahrenheit is °F and it is measured in degrees. The difference between the freezing point and boiling point of water is 180 fahrenheit degress where the boiling point of water is 212 °F and the freezing point of water is 32 °F. This means that one degree on the fahrenheit scale is 1/180th of the difference between the freezing and boiling point of water. (ice point and steam point)
On the celsius scale the difference between the ice point and steam point of water is 100 celsius degrees. The fahrenheit and celsius scale coincide at -40 degrees which means that -40°F and -40°C describe the same (very cold) temperature.
If you want to know more details about the farhrenheit scale you can read about it in the Wikipedia where these sort of things are well documented. Fahrenheit on the Wiki.
Fahrenheit is used in the US today and it was used in most English speaking countries until the 1970's when the celsius scale was introduced as part of the effort to shift everything to metric measures.