In lighting terms, Class refers to the protection against potential electric shocks that can happen due to physical contact with the electric part of the device, differentiating the type of connection between the protection and ground. Generally, in lighting, the equipment are divided in three different classes and each one of them is associated to a different icon:

The device is ground connected using a protective conductor. This conductor generally is green or green and yellow and it will avoid the electric shock when in physical contact with the electric part of the device.

The device has a double layered electric isolation, having no need, in general, of the protective conductor like in Class I devices. This double layered isolation works as a protection against electrical shocks when in physical contact with the electric part of the device.

The device uses low voltage to avoid all possibilities of electrical shock when in physical contact with the electric part of the device.