Let's get the basic definitions out of the way. WMIC is the name of a tool and it stands for Windows Management Instrumentation Command. The command part refers to a command line interface; presumably, WMICLI was deemed too long. The tool allows us to perform WMI operations. WMI is the Windows infrastructure for operations and management data. In addition to providing management data to other parts of Windows and other products altogether, it's possible to automate administrative tasks both locally and remotely with WMI scripts and applications. Often, administrators access this interface through PowerShell. Like all the other topics in this book, a proper treatment of all the power available to you via WMIC is out of scope for this discussion. There are great resources online and in bookstores for the curious reader.
For now...