What is the input offset voltage of an op-amp?

In the case of the ideal op-amp, the DC voltage of the V_IN(+) and V_IN(-) terminals match exactly when the input voltage (V_i) is 0 V. In reality, however, there are differences in input impedance and input bias current between the V_IN(+) and V_IN(-) terminals, causing a slight difference in their voltages. This difference called input offset voltage is multiplied by a gain, appearing as an output voltage deviation from the ideal value.
When used in amplifiers of sensors, etc., the input offset voltage of an op-amp results in an error of sensor detection sensitivity. To keep sensing errors below a specified tolerance level, it is necessary to select an op-amp with low input offset voltage.