Otherwise, the operating system needs to be activated by Microsoft. If both the IDs are close to each other, then the operating system assumes that it is running on the same device.
Every 10 days and after every reboot, a new HWID is generated which is compared with the one generated at the time of installation. This identifier represents all the hardware devices attached to the host computer and is transferred to Microsoft. A string called a Hardware Identifier (HWID) is generated by the operating system when it is installed for the first time. Hardware identification is a security measure used by the Windows operating system on activation. Techopedia Explains Hardware Identification
