All network devices have a MAC (Media Access Control) address that uniquely identifies the device and are integral to network communication. This address is permanent and is assigned when the device is manufactured. Mac addresses consist of 12 alpha-numeric characters separated by colons (ex: a3:49:2c:03:88:4f ). Only the letters A though F are used, and upper/lower case doesn't matter so you don't have to worry about confusing the number 0 with the letter O. Sometimes the colons are replaced by dashes, other formats are less common, but also used.
MAC addresses have nothing to do with Macintosh / Apple / Mac computers. Anything that connects to the internet via WiFi or ethernet cables will have a MAC address. PC's have them, smart phones have them, gaming consoles have them. In general, if it connects to the internet you can assume it has a MAC address.
While the acronym MAC is becoming the standard term, some other words or terms are sometimes used instead. WiFi address, Physical Address, Hardware Address, Burned-in Address (BIA), Ethernet Hardware Address (EHA), and a handful of other terms are used. Regardless of what it is called, it will always consist of 12 alpha-numeric characters.
If you're still curious about MAC addresses and how/why we use them a quick internet search will turn up even more in-depth information.