Domestic devices transfer energy from a supply to the stores where it is useful. A battery has energy in its chemical store. When a battery is connected to a motor, as in a toy car or a cordless drill, energy is transferred electrically to the motor, which transfers it to the kinetic store of the moving parts. Some energy is also wasted as heat.
Mains devices use the a.c. mains supply. A kettle, a toaster and an electric heater have a heating element, a wire with a high resistance. Energy is transferred electrically to the element, and the element transfers it to the thermal energy store of the water, the bread or the air.
Some devices do both. A hairdryer has a motor that turns a fan, so energy is transferred to the kinetic store of the fan, and it also has a heating element that warms the air passing over it. Whatever the device, the energy transferred is measured in joules (J).