What does Fair Trade guarantee? As a result of my social environment, i always buy coffee that has the Fair Trade label.
Of course it means i spend some extra cash that goes to the coffee producing farmers in exotic countries.
But i would like to know what the organisation is, that supervises the coffee trade, and what exactly the label guarantees.
If you mean the coffee bean farmer by 'end-producer',
Fair Trade guarantees a relative increase of the contract that the farmer can negotiate. 

Say, for example a farmer gets USD 20,- for his entire crop usually, then

He might get USD 140,- for the same amount of beans when selling to a Fair Trade contracter. 
Also see: How much do the farmers get about prices in Ethiopia.