Op-amps need the power supply to drive for application. One is positive power supply VDD and another one is negative power supply VSS. We also can choose ground as VSS.
In order to make op-amps work in the right functions, the voltage difference between VDD and VSS must stay in a certain range, otherwise, it may not operate as expected.
Quiescent Current is the amount of current consumed by op-amp when it is not performing any work. Low quiescent current is an important characteristic of op-amps. Especially for a battery powered application, it will affect the battery life.
When added a load to an op-amp, the current into VDD pin primarily goes through the op-amp output stage and then through the load. Normally, the internal integrated circuit of op-amp includes three stages. The first stage is a differential stage. The second stage is the high gain stage and finally the third stage is the very low impedance output stage.
The picture below shows the MCP601 power supply specification.