IP ratings use a 2 digit system to designate the environment rating of the enclosure. The first digit specifies the protection from solids and the second digit specifies the protection from water.

IP. First digit:
Ingress of solid objects.
Second digit:
Ingress of liquids.
0 No protection. No protection.
1 Protected against solid objects over 50mm e.g. hands, large tools.
Protected against vertically falling drops of water or condensation.
2 Protected against solid objects over 12.5mm e.g. hands, large tools.
Protected against falling drops of water, if the case is disposed up to 15 from vertical.
3 Protected against solid objects over 2.5mm e.g. wire, small tools.
Protected against sprays of water from any direction, even if the case is disposed up to 60from vertical.
4 Protected against solid objects over 1.0mm e.g. wires.
Protected against splash water from any direction.
5 Limited protection against dust ingress.
(no harmful deposit)
Protected against low pressure water jets from any direction. Limited ingress permitted.
6 Totally protected against dust ingress.
Protected against high pressure water jets from any direction. Limited ingress permitted.
7 N/A
Protected against short periods of immersion in water.
8 N/A
Protected against long, durable periods of immersion in water.
9k N/A
Protected against close-range high pressure, high temperature spray downs.

If you are looking for a comparison of NEMA and IP ratings, see our Control Panel Environmental Ratings NEMA and IP lesson.