Imagine you have a “No name brand” Ethernet card, without a driver disk or CD.

You plug it into your computer, and Device Manager can’t find the drivers for it.  If you get the Vendor ID and the Device ID from the Hardware ID Property Field in Device Manager:
Device Manager

And then you take those ID’s; and do a search with the Device ID on

After you press Search, you get results like these:

You can see multiple devices were returned for Device ID 1681.  But if we check the Vendor ID, we can see we have a Broadcom 57xx Gigabit Integrated Controller.  So we can now go to the Broadcom site and grab the correct Ethernet driver.