The IP degrees of protection (ingress protection) are defined by the International Electrotechnical Commission in its IEC 60529 standard. These protection classes classify the degrees of protection of unprocessed housings of electrical devices with a rated voltage of maximum 72.5 kV. (IEC standard 60529 as well as DIN EN 60529; VDE 0470-1:2000-09)
The abbreviation IP is followed by two digits. The first digit stands for protection against the penetration of solid bodies. The second digit describes the degree of protection against the ingress of water. The numbers have specific descriptions, which you can find in the tables.
For example, a roda Rocky RK12 meets the IP65 protection class. This means full protection against contact with live components or internal moving parts. It also provides protection against the ingress of dust and water jets from nozzles, directed against the Rocky from all directions.