Responsive web design
Sometimes abbreviated as RWD, responsive web design is method of creating webpages so that they adjust to the device viewing the document. For example, when a user views a website on a desktop computer, they often have a large screen with 12 to 18 point font. However, when this same site is viewed from a smartphone or tablet, it is scaled down. Even though the screen may be closer, the content is smaller. Therefore it would need to be adjusted so that the user could have a better browsing experience.
How does it work?
Responsive web design uses percentage measurements for HTML elements so they scale appropriately, rather than at the fixed measurements. Additionally, the @media rule is used to call special CSS settings based on the device; usually depending on the width of the browser.