The IP code or Ingress Protection code indicates how well a device is protected against water and dust. It is defined by the International Electrotechnical Commission (IEC) under the international standard IEC 60529[1] which classifies and provides a guideline to the degree of protection provided by mechanical casings and electrical enclosures against intrusion, dust, accidental contact, and water.

Blah, blah,blah right?  In short, it is a dust and waterproof rating.

When something is claimed as "waterproof", that can be a vague description right?  An IP Rating adds an index for you to compare products.

In marketing terms such as waterproof, a cellular phone rated at IP67 is "dust resistant" and can be "immersed in 1 meter of freshwater for up to 30 minutes".  If product (A) is advertised as waterproof and IP65 and product (B) is advertised as IP69k, then product (A) is going to be the highest water and dust proof ratings.  The rating is most certainly important to evaluate what you are getting and what you can safely do with the product.

The most common IP Ratings that you will see in our industry:

IP65
IP67
IP68
IP69(k)

IP65 - Offers protection for water with:

Water jets  Water projected by a nozzle (6.3 mm (0.25 in)) against enclosure from any direction shall have no harmful effects.

Test duration: 1 minute per square meter for at least 3 minutes Water volume: 12.5 litres per minute

Pressure: 30 kPa (4.4 psi) at distance of 3 meters (9.8 ft)

IP67 - Offers protection for water with:

Immersion, up to 1 meter (3 ft 3 in) depth.

Ingress of water in harmful quantity shall not be possible when the enclosure is immersed in water under defined conditions of pressure and time (up to 1 meter (3 ft 3 in) of submersion).

Test duration: 30 minutes. Tested with the lowest point of the enclosure 39in below the surface of the water, or the highest point 5.9in below the surface, whichever is deeper.

IP68 - Offers protection for water with:

Immersion, 1 meter (3 ft 3 in) or more depth

The equipment is suitable for continuous immersion in water under conditions which the manufacturer shall specify. However, with certain types of equipment, it can mean that water can enter but only so that it produces no harmful effects.

The test depth and duration are expected to be greater than the requirements for IP67, and other environmental effects may be added, such as temperature cycling before immersion.

Test duration: agreement with the manufacturer Depth specified by the manufacturer, generally up to 3 meters (9.8 ft)

IP69(K) - Offers the highest degree protection for water with:

Powerful high-temperature water jets.  For uses with high pressure washing & cleaning. (Pressure Washers)

Protected against close-range high-pressure, high-temperature spray downs. Smaller specimens rotate slowly on a turntable from 4 specific angles. Larger specimens are mounted in the intended position when used, no turntable required, and are tested freehand for at least 3 minutes at a distance of 0.15–0.2 meters (5.9 in – 7.9 in). The specific requirements for the test nozzle are shown in figures 7, 8, & 9 of IEC (or EN) 60529. This test is identified as IPx9 in IEC 60529.

Test duration: Fixture: 30 sec. in each of 4 angles (2 min. total), Freehand: 1 min/m2, 3 min. minimum Water volume: 14–16 liters per minute (0.051–0.059 impgal/s) Pressure: 8–10 MPa (80–100 bar) at distance of 0.10–0.15 meters (3.9 in – 5.9 in) Water temperature: 80 °C (176 °F)