Watt is one of the most well-known units for light and electricity. It indicates the power or energy consumption of a device. Technically, the power in watts is calculated by dividing the work done (in joules) by the time (in seconds).

The term wattage is not formally correct, but it is commonly used to refer to the energy consumption of a lamp or device.

In short: the higher the wattage, the more energy the device uses or the brighter a lamp can shine.