In CSS context, a screen is a (visual) media type that is intended primarily for color computer screens.
A user agent on a screen generally impose a minimum width and choose an initial width based on the dimensions of the viewport.
See also Screen
The CSS resolution is always given in Css Pixel (not in Hardware pixel)
The CSS screen resolution is determined by:
Example:
<MATH> \text{Maximum Width in CSS Pixel} = \frac{\displaystyle 1920}{\displaystyle 2} = 960 </MATH>
Why would the same page look different on the screens with identical resolutions ?
In Google Analytics, you can find the screen resolution at Audience > Technology > Browser > Screen Resolution