Responsive web design is the approach that suggests that design and development should respond to the user’s behaviour and environment based on screen size, platform and orientation. With new devices of varying screen resolutions cropping up regularly, it is essential to have web design that adapts itself to multiple screen sizes.
Source: http://www.mobimanage.com/
See also:
- Structure of a Responsive Mobile Web Design [Infographic]
- How to Grow Your Mobile Presence [Infographic]
- Should You Build a Mobile App or Mobile Website? [Infographic]