In non-inverting amplifier, the input voltage V1 is feed to non-inverting input terminal.  The current I1 through the resistance R1 is given by 
I1 = VB/ V1

The current through the feedback resistor R0 is given by
 Vout = 1+ R1 
 Vin           R1 

Where gain of the non-inverting amplifier is
1+ R1 
    R1

The gain depends upon the resistance R1 and R0. The input impedence of the amplifier is very high as practically no current flows through the input source V1.