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 a bit closer, the content is much 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.