What is a transfer bar and what should it do in a properly functioning firearm?

The transfer bar is a type of internal safety that sits between the hammer and firing pin. When the trigger is pulled the hammer will cock while the transfer bar is raised in place to allow the energy of a falling hammer to transfer to the firing pin so it may strike the primer and fire the ammunition. When de-cocking the hammer and keeping the firearm pointed in a safe direction pulling but then releasing the trigger you allow a controlled drop of the hammer, and the transfer bar will drop out of place so if the hammer slips it will not contact the firing pin.