I can't find this answer anywhere, so I thought the only place I can resolve this question is here.
Most sources agrees RWD is an "approach in CSS", but what exactly would does it mean (is it just a way to build a web page?) .
What would be other approaches then (aside form mobile first / desktop first, which I consider inside Responsive Web Design).
If is a way of building/designing with CSS then aren't "good CSS practices" the same, whats the difference?