Windows on iMac?

If this is an Intel-based Mac:

You can run regular Intel versions of Windows. You have two options:

• Installing Windows as a "dual-boot" operating system, with the aid of Boot Camp. This means that at any one time, you'll either be running macOS (only) or Windows (only) – you'll have to reboot to switch. An advantage is that when you're running Windows, you won't have the overhead of running two OSes at the same time.
• Installing Windows as a guest operating system inside of a Parallels or VMware Fusion virtual machine.

If this is an Apple-Silicon-based Mac:

You can't run regular Intel versions of Windows. You can only run Windows 11 for ARM. It is happiest when running Windows applications that have been rebuilt for ARM. There are a few of those (e.g., Adobe applications), but not a lot. Windows for ARM can run many off-the-shelf Windows/Intel applications, using its own emulation or translation code (think: Microsoft's version of Rosetta 2), but there are some limitations to this (as with Rosetta 2).

Apple doesn't support Boot Camp on Apple Silicon Macs. (And when Apple Silicon Macs first came out, Microsoft wasn't officially supporting the use of Windows for ARM on Macs in ANY form.)

So your options come down to running Windows 11 for ARM inside of a Parallels or VMware Fusion virtual machine.