This is a "transimpedance amplifier"--an amplifier with a current input and a voltage output, constructed using an op-amp.  Since the input current to the op-amp is zero, the current in the feedback resistor has to be equal to the input current.  The op-amp provides the output voltage necessary to equalize these currents with the inverting input voltage held equal to the non-inverting input voltage (which is zero since it's tied to ground).

This type of amplifier is often used in optoelectronics, because photodetectors are typically operated so as to produce a current output that then must be amplified.