RWD uses so-called breakpoints to determine how the layout of a site will appear: one design is used above a breakpoint and another design is applied below that breakpoint. The breakpoints are commonly based on the width of the browser.
Commerce is the conduct of trade amongst economic agents. Generally, commerce refers to the exchange of goods, services or something of value, between businesses or entities. From a broad perspective, nations are concerned with managing commerce in a way that enhances the well-being of citizens, by providing jobs and producing beneficial goods and services.