Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
From Office 2013 on wards only 365 versions can be installed on multiple PC/Mac's
Lifetime license versions are licensed for the single working installation
When purchased during the install/setup process the key is used in the creation of an MS Account, after which the key cannot be re-used and you reinstall via that MS Account.
Only Office 2010 H&S, or earlier versions, were licensed for 3 working PC's