A transfer function is a way of describing the linear differential equation of a system. If the system has no feedback it is an open loop system and possesses an "open loop transfer function". If the system has feedback, for example the fly-ball governor on a steam engine, then it is a closed loop system and possesses a "close loop transfer function".
You mean you are interested in the isomorphisim between the algebra of rational polynomial functions and the solution of linear differential equations by the LaPlace transform method. Mon Dieu! Incroyable!
"Whatever" is the magic word of death that eliminates all possibility of further communication. There will be no duck dropping down and there will be no prize either. So sorry Charlie.