Revision 14. This usually implies a community-made or enterprise-specific build that has undergone 14 iterations of optimization or software integration. w10pro: Windows 10 Professional edition.
The version of Windows 10 (the final major feature update for the OS). x64: 64-bit architecture. iso: The file format, which is a disk image. Why is it 421 GB? download upd rev14w10pro22h2x64iso 421 gb
To summarize: