Windows Management Instrumentation (WMI) is a set of extensions to the Windows Driver Model that provides an operating system interface through which instrumented components can provide information and notification. WMI is Microsoft's implementation of the Web-Based Enterprise Management (WBEM) Standard from the Distributed Management Task Force (DMTF).

What this really means is that each host computer contains a set of information you can poll to gather data on your network assets.

If all of the devices connected to a subnet are members of a Windows domain, you can use LDAP to gather information. But if the network is peer-to-peer, or running other networking software such as Novell, you will need an alternative.

WMI inqueries allow you to gather literally hundreds of pieces of information about the hardware and software configurations of hosts.

Microsoft's Technet provides an exhaustive description of data fields and implementation.