Outside of programming device drivers, knowing the globally unique identifier (GUID) for a hardware device class is useful when looking up driver information in the Windows registry.
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For example, the solution to various error codes in Device Manager is to delete specific registry values from registry keys named after a device's GUID.
A globally unique identifier (GUID) is just that: a unique number used in this context to identify specific hardware components. Windows creates the GUID, written in hex as a 128-bit alphanumeric string, for each piece of hardware. A GUID starts with one set of eight hexadecimal digits, followed by three groups of four digits, and then one group of 12 digits.
