If you are not familiar with them, power pads are small pieces of leather that are installed on the center main strings at the throat of the racquet. Their purpose is to reduce stress on the string where it would contact the frame or grommet strip. They are primarily used to provide cushioning when stringing natural gut.
While power pads may protect the string, they provide few, if any, performance benefits for the player. Pojies on the other hand, can protect your arm, enlarge your racquet's sweetspot, and give you a deeper ball pocket.