There are different ways of 'resetting' a computer, with varying effects.
However, in general, if you do a 'factory reset', you'll be left with the Windows operating system on your computer and possibly any other software that came pre-installed. However you'll lose all of your documents, photos, videos and other files that you've created or downloaded (although you can, of course, back those up to a USB memory stick, or elsewhere, before carrying out the reset). You'll also lose any software that you've installed yourself. (You can't back that up. You'd have to reinstall it after the reset).
I've been using Windows computers for a quarter of a century, usually owning two or three at a time. During that period I've hardly ever needed to restore a computer back to its 'out of the box' settings. It's definitely NOT something that should be done routinely!