Every device that connects to an ethernet based network has a MAC address associated with it’s network card (NIC). The MAC address is used in layer 2 communications between devices and generally consists of 6 hexadecimal pairs separated by hypens, colons or in some cases, dots.
The first 3 hex pairs are assigned to the device manufacturer by the IEEE. The second 3 pairs are assigned to devices by the manufacturers themselves.
As a network engineer, it can be extremely useful to know which manufacturer is associated with a MAC address when troubleshooting issues on a network and this is where the Wireshark OUI database comes in handy.
One of the best databases available is the Wireshark OUI database which can be found here: https://www.wireshark.org/tools/oui-lookup.html