What is a Responsive Website?
Jargon: Responsive web design is an approach to designing and developing applications and websites that detects the user’s screen size, platform and orientation and changes the layout accordingly. At a minimum it includes flexible grids, images and intelligent use of CSS media queries, but in a more practical sense, it goes into all aspects of development and design adapting the user experience based on device, size, browser version, OS version, and so forth.
Simple: A responsive website is one that is built on a fluid scale (percentages) and adapts depending on the device displaying the website so that the user has the best experience possible on that device without having to create separate websites for every device — no more pinching and zooming!
Who doesn't like responsiveness? It just sounds nice… and besides, Google now compels it!
Next Up: 1.3 - Information Architecture