Emergency light is lighting for an emergency situation when the main power supply is cut and any normal illumination fails. Emergency lighting is normally required to operate fully automatically and give illumination of a sufficiently high level to enable all occupants to evacuate the premises safely.
An exit sign is a device in a public facility (such as a building, aircraft or boat) denoting the location of the closest emergency exit in case of fire or other emergency. Exit signs are designed to be absolutely unmistakable and understandable to anyone.