how does mac isight camera work on windows7/10

If you are referring to the built-in camera on a MacBook Pro then this implies you are running Windows via Boot Camp. If so then I believe normally this driver should be installed as part of the Apple Boot Camp driver pack.

Note: The original built-in camera was referred to as an iSight camera but was then referred to as a 'FaceTime' camera and is now referred to as a 'FaceTime HD' camera.

An updated FaceTime camera driver for Windows is available here - FaceTime Camera Driver Update

However I would check and make sure you have the current Boot Camp drivers from Apple installed first. As part of this it should also have installed Apple Software Update in to your Windows so it can check for updates.

I use a Mac mini for Boot Camp so it does not have such a camera and hence I cannot check this.

The FaceTime camera is a USB device, in theory this means you can use Parallels Desktop or VMware Fusion to run Windows and 'share' the camera i.e. that USB device from the host Mac environment in to the virtualised Windows environment.

Most Mac laptops have built-in iSight (or FaceTime) cameras. There is an older Firewire iSight that was used with older Macs and Minis.

Check under Device Manager and look for FaceTime camera, if you are using the built-in camera. Here is an example.