A difference amplifier model is a OpAmp circuit model, capable of amplifying the weighted difference between the two input signal at the amplifier input. The signal with the higher potion, will refine the output signal sign. Example, if the magnitude of the non-inverting signal is higher than the inverting one, then the output will be positive, negative otherwise. You may try changing the amplitude of each input signal individually, and you will notice this functionality. Have fun!
