The second plate in a parallel plate capacitor serves multiple important functions. It provides a surface for charge separation, helping to accumulate opposite charges on each plate when a voltage is applied. This charge separation creates a uniform electric field between the plates. Additionally, the second plate effectively lowers the potential of the first plate, allowing more charge to be stored on the capacitor. In essence, it acts as a conducting neighbor to the first plate, increasing the capacitor's overall capacitance and enabling it to store more electrical energy.
