Body element (red border; no width set, implicit width of 100%) + div element (blue boder; 330px width).

The viewport meta tag is set. The layout viewport width will be set at 660px.

On a phone with about 400px visual viewport width (e.g. Pixel 2), the scale factor is 400/660 = 0.6.

The page body (red) will occupy the whole screen width and the div (blue) will occupy about half (330/660).

Compare this with 2-330px-meta.html on a mobile device.