IP Rating definition/explanation

The IP (Ingress Protection) rating presents the level of protection a light fixture has against dirt and water.

Any fixture that is used in a bathroom, wet environment or outdoors should have an IP rating that is high enough to stop dirt or water entering the fixture, as to protect it from being damaged.

An IP rating consists of two digits. The first digit represents protection against the ingress of solid objects, and the second digit represents protection against the ingress of liquids. The higher the value of either digit, the greater the protection.

Please see this Blog for more details about IP in Bathrooms.