You may need the architecture (x64/x86(x32)) of your Windows system for various apps and tools that are used for various web hosting/domain management.
To check which version of Windows you have, click the Start Menu icon: Type in: "This PC": Hit ENTER. Similar window should pop up: Right-click anywhere inside the window, like so: Click on Properties: Once you've done that, you will see a Window open with the information you need:
Your version of Windows and your architecture type are both defined here:
And you're done! Take a look at the underlined details. Most of the time you will need the bottom lines, which define your Windows/CPU architecture type.