Read this article online.

Power supplies are usually intended to generate a fixed, stable output voltage. The output must not oscillate, and it should remain constant with load transients and changes in the input voltage. To optimize the control loop of a switch-mode power supply, compensation pins are present in many power-supply ICs.

These pins can be wired with appropriate compensation components, capacitances, and resistors to optimize the control loop to achieve the highest control bandwidth while ensuring loop stability. The control loop is adjustable because the compensation needs to be approached differently depending on the operating conditions and the selection of external components in the power supply’s path. Figure 1 shows a buck regulator with a corresponding compensation pin, VC.