Power is the energy transferred per second. It tells us how quickly a device transfers energy. Power is measured in watts (W), and 1 watt is 1 joule per second.
A 60 W lamp transfers 60 joules of energy every second. A 2000 W kettle transfers 2000 joules every second, so it has the greater power and transfers energy more quickly. Large powers are often given in kilowatts: 1 kW is 1000 W, so a 2 kW kettle is a 2000 W kettle.
Power is about the rate of transfer, not the total amount of energy. A low power device left on for a long time can transfer more energy in total than a high power device used for a short time.