the.com/viewport
The window your screen pretends is the whole internet.
means The visible area of a web page on your device, before any scrolling reveals the rest.
from Borrowed from aviation and 3D graphics, where a viewport was the literal frame you saw the world through; the web stole it to mean the browser's visible slice.
Meta tagOne line tells phones to stop lying about width.
Unitsvw and vh measure space relative to it.
Not the pageIt is the keyhole, not the room.