These represent the feature update cycles for Windows 10.
You still need a valid Windows license key to use these versions legally. How to Proceed Download Windows Lite Version 21H2 21H1 Build 1904X 1387 zip
Because these are created by third parties, they do not come from Microsoft. There is a risk that the ISO could contain malware or that essential security patches have been disabled [4]. These represent the feature update cycles for Windows 10