An ISO file (ISO 9660 standard) is an archive file that exactly replicates an optical disc (CD, DVD, or BD). When you download a Windows 10 ISO, you are getting a single file that contains all the folders and data needed to install Windows—just as they would appear on a physical installation DVD.

The ISO file downloaded from Microsoft is and can be installed without a product key (it will function as an unactivated version with some limitations, like a watermark and inability to personalize settings). To fully activate Windows 10, you will need to purchase a genuine product key from Microsoft or an authorized retailer.

The “64-bit” designation refers to the processor architecture the operating system is designed for.

: This is the standard method for Windows users. You download a small executable from the Microsoft Software Download page that guides you through creating a bootable USB or saving the ISO to your drive.

Using the ISO and a free tool like or the Media Creation Tool, you can create a bootable USB to install Windows on one or multiple machines.