Responsive web design (RWD) is a web design approach aimed at crafting sites to provide an optimal viewing experience—easy reading and navigation with a minimum of resizing, panning, and scrolling—across a wide range of devices (from mobile phones to desktop computer monitors).
It is important for new communications sites to be responsive because the greatest growth in internet connectivity is coming from mobile users, with close to 90% of all new connections coming from mobile users.
it is therefore important for a new web sites to be easily viewable both on a desktop screen as well as a mobile phone.