Responsive design allows websites to be viewed on any device by automatically adjusting layouts. The document discusses creating large-scale responsive websites that serve both desktop and mobile users well. It defines responsive design as providing complete content across all devices and connections using a single URL. While technical aspects like fluid grids and media queries are important, usability must be a top priority through efficient and effective layouts on mobile. The strategy discussed is to make responsive design the standard, focus on modern browsers and devices first, and introduce changes in phases.