Responsive Web Design(rwd) is an approach to web design intended to make the viewing and use of web pages easier across multiple platforms and devices, ranging from smart phones to desktop computers, by utilizing technologies that are present on those devices and selectively omitting or replacing features which would be cumbersome without certain technologies.
Without certain features, like a large display or a mouse, traditional websites with rich content can be cumbersome for the user, if they are usable at all. Poorly designed sites will sometimes not render properly at all on mobile browsers.
RWD, as a principle feature, means only showing a user content they can use. Some RWD techniques include smaller numbers of items per page, larger text, fewer images and accessory components, and generally fewer links.