WWN - Worldwide name, this is a unique identifier in a Fibre Channel storage network.
Each WWN has a fixed 64-bit name assigned by the manufacturer and registered with the IEEE to ensure that it is globally unique. It may only include characters from A to F, a to f, digits from 0 to 9 and the : character. You can find the WWN in your HBA card manual, BIOS or directly on the HBA card label.
Example of WWN: