With some Office packages there is a choice between device-bound and account-bound. For example, Microsoft Office 2021 Professional Plus.
Device-bound: No Microsoft account required. In this case, the software is bound to one device. It is not possible to use it on another device. However, you can reinstall the software on the same device, provided no changes have been made to the hardware. If the hardware is changed, e.g. if the hard disk is changed, the device is recognised as a new device and therefore the Office package cannot be reinstalled.
Account bound: Microsoft account required. The account-bound version requires a Microsoft account. The software is registered via this account and the licence is permanently stored there. The software can be used on one device. If you change your hardware, you can download the software again via your Microsoft account and install it again. Even if you change devices, the software can be reinstalled and activated at any time.
As a customer, you must ultimately decide for yourself which version makes the most sense for you. In terms of price, the device-bound version is somewhat cheaper. Many customers prefer the device-based version, as it does not require a Microsoft account. Both versions have their advantages and disadvantages.