CONCEPT
Design is the 'how' and 'why' people want to use the site; the speed at which the site loads; the interaction between hover, click and touch; and the pace at which you deliver new features and content. All of these concepts comprise design.
HTML + RESPONSIVE
Responsive Web Design makes your web page look good on all devices (desktops, tablets, and phones).
Responsive Web Design is about using CSS and HTML to resize, hide, shrink, enlarge, or move the content to make it look good on any screen.