Viewport concepts presents conflicting definitions and odd language

### MDN URL

https://developer.mozilla.org/en-US/docs/Web/CSS/Viewport_concepts

### What specific section or headline is this issue about?

Viewport concepts

### What information was incorrect, unhelpful, or incomplete?

The articles seems to mix up ideas and provide conflicting definitions.
E.g.

> - On larger monitors where applications aren't necessarily full screen, the viewport is the size of the browser window.
> - On most mobile devices and when the browser is in fullscreen mode, the viewport is the entire screen.
> - In fullscreen mode, the viewport is the device screen, the window is the browser window, which can be as big as the viewport or smaller, and the document is the website, which can be much taller or wider than the viewport.

Additionally, some of the language form is rather odd/awkward, e.g.

> width of the outside of the browser window including all the window chrome.

### What did you expect to see?

Clear explanations of the main concept of the article, if using/explaining other terms/concepts, linking to their definitions and/or using them in consistent way. Simple and grammar-correct language use.

### Do you have any supporting links, references, or citations?

_No response_

### Do you have anything more you want to share?

_No response_