Body element (red border; no width set, implicit width of 100%) + div element (blue boder; 1200px width).

The viewport meta tag is NOT set. The layout viewport width will be set at 1200px (as 1200 > 980).

On a phone with about 400px visual viewport width (e.g. Pixel 2), the scale factor of 0.3 (400/1200) will be applied. The page looks smaller.

The page body (red) will occupy about 5/6 of the the whole screen (about 980/1200) and the div (blue) will occupy the whole screen (1200/1200).

Compare this with 4-1200px-meta.html on a mobile device.