On the C: drive, what is the difference between the Program Files folder and the Program Files $($x$86)$ folder?

answer

Program Files keeps $64-$bit files, while Program Files $($x$86)$ keeps $32-$bit files.

Program Files keeps the limited version files, while Program Files $($x$86)$ keeps the extended version files.

Program Files keeps $32-$bit files, while Program Files $($x$86)$ keeps $64-$bit files.

Program Files keeps $.$exe files, while Program Files $($x$86)$ keeps $.$msi files.