how to design nonlinear feedforward control system in simulink?

I am trying to learn difference between PID controller in control system and Nonlinear feedforward controller in control system.I wanna see these difference on graphic and i wanna do two block diagram on simulink.But i am new on control systems so i couldnt do anything or i couldnt find anything.So can you please give me some examples about it , or tell me how can i design it because i couldnt find anything useful for beginners.