Serial number
From WLCS
Serial Number
Technical Definition
A product's serial number is a number, or string of symbols, that are assigned to the product to set it apart from every other instance of that product. This makes each one identifiable and are almost always non-negative.
In Layman's Terms
The serial number is what makes every product unique.
Examples
The serial number for your hardware device can usually be found on a sticker with the manufacturer's name and logo.