Duduli

It is defined as the voltage available at the output terminal of an op-amp when no input signal voltage is applied. For ideal op-amp output offset voltage is zero while for practical op-amp the output offset voltage is non-zero.    

In inverting amplifier the input signal voltage is applied to the inverting input terminal of op-amp & the non-inverting input terminal is grounded.

Common mode rejection ratio is defined as the ratio of differential input signal to the voltage gain for common mode input signal.

An operational amplifier (op-amp) is a circuit that can perform mathematical operation such as addition, subtraction, differentiation & integration.

A differential amplifier is a circuit that can accept two input signals and amplify the difference between these two input signals. Look at the figure