Kelvin is the SI base unit for temperature and is has the symbol K.
Kelvin is named after 1st Baron Kelvin, William Thomson who was born in Belfast and studied engineering and physics at Glasgow University.
The scale was based on Lord Kelvin's theory whereby a) there was a need for "absolute zero" or "infinite cold" to be represented by 0 and b) used degree Celsius to increment each unit.
The Kelvin has also been adapted to measure colour temperature and noise temperature; both with the capability to express amounts of "warmth". The photosphere of the sun, for example, has an effective colour temperature of 5778K.
Farenheit (or degrees Farenheit) is a scale to measure temperature and is part of the imperial / US customary unit system with the symbol °F.
The Farenheit scale was proposed in 1724 by Daniel Gabriel Farenheit and was the first standardized temperature scale to be widely used.
0 °F was set as the freezing point of a solution made from equal parts ice, water and salt. It was then established that the melting point of ice was 32 °F and human body temperature was 96 °F (or 98.6 °F when the scale was redefined into the modern version of the scale).
It is still used in the US and some associated territories as the official temperature scale. Everywhere else in the world uses Celsius.