Why does landscape Media Query work on my computer when browser isn't "landscape"?

I’m wondering about the media query that requires specific screen widths and landscape orientation, the example here:

The lesson says that the definition of landscape is when the width is larger than the height. But when I resize the width of my browser, the browser window quickly becomes taller than it is wide. so why does the media query still apply?

Does orientation apply to the device screen, but width/height applies to the browser window?