How to factory reset Mac Mini

Follow the steps here:

What to do before you sell, give away, or trade in your Mac - Apple Support

If you are not selling it you may want to just follow Step 6.

This is same for all iOS devices including Mac Mini

Shut Down

While Restarting Hold down Command and R keys

You will enter recovery mode

You will have four options.

Re-install MacOS will erase all data and Reinstall the entire OS.

madhufromjamshedpur wrote:

This is same for all iOS devices including Mac Mini

...

The Mac Mini is not an iOS device. In fact, no Mac is an iOS device.

iOS devices by definition run iOS. Those are iPhones, iPads, and iPod touches.

See here: How to erase macOS from macOS Recovery - Apple Support

Thanks for the explanation in detail.

I am correcting myself all Mac uses Mac OS including Mac Mini.