It’s account bind license key which means license key will link with your Microsoft account so even after hardware changes it still works and u can transfer it to another pc also.
POINTS
 🔸100% updatable | Runs on windows 10 or later edition only. 
🔸Safe Online Activation
🔸Genuine Windows Software
🔸Official Download Link Provided
🔸Instant delivery after purchase by email.
🔸License key bind with Microsoft account.
 
Attention! Office 2021 only runs on Windows 10 and Windows 11 operating systems The key needs to be used only on one device.
Activating the key and downloading the distribution kit on the official website setup.office.com