IP44 and IP65

IP44 is a common designation for lighting.

4 - as the first digit means anything smaller than 1mm in size will not get through the membrane.
4 - as second digit means resistant to water splashes.

IP44 cannot be used when there is exposure to water jets (but not high pressure or high temperature water jets)

IP65 is the recommended minimum requirement when water jets are involved.

Bulbs without IP markings are by default IP20 which means protection from solid objects but no protection from water.

What is an Ingress Protection rating?

An IP rating (or IP code stands) for "Ingress Protection Rating" which classifies the level of protection electrical appliances have against intrusion of solid objects, dust and water.

The standard aims to provide more information than simple "waterproof".

The first digit indicates the amount of protection against solid objects.

The second digit indicates the protection of the equipment inside against various forms of moisture.

e.g. an IP65 halogen shower light will have a protection-versus-solids rating of 6, which indicates its dust-tight, and protection-versus-moisture means protection from water projected from a nozzle. IP67 would mean protection against immersion in water, and 68 would be complete continuous immersion in water (but submersion depth and time must be specified).