What is the feedback topology in the given circuit ??
At the input i can see that input and feedback currents are mixing, but what quantity is being sampled at the output here.      
Is it voltage  because i am getting  If = -Vo / Rf    
or is it current because    i am also getting  Io= -If......... ??
pls help i am confused

Hi,
Nothing is mixing. If case of an ideal amplifier, source current equal exactly to feedback current. Since voltage at the inverting input is a virtual ground, it is equal to DC, whatever current your apply to it i.e input impedance is zero. Consequently, input for this configuration should be a current. Voltage does not make sense, since it would be similar to connecting voltage source to ground.

Output of the amplifier is the only way for current to flow. So output voltage is defined by Rf and input current. If you apply a current source to the output you will see that this does not affect the output voltage. Therefore the output impedance is zero, i.e there is a voltage at the output.

So, this is a current input- voltage output amplifier.

voltage sampling at the o/p and voltage mixing at the i/p.
please have a look into razavi basic micro-electronics.

Thanks,
Raj.

time to buy a few textbooks!