In simple terms, a responsive website automatically adjusts to fit a tablet, desktop, laptop, or Smartphone. These responsive designs make a user's experience more enjoyable, convenient and effective.
Both Nielsen and Pew Research Center's Internet & American Life Project have said that more than half of cell phone users access the internet on their phones. You can probably expect that percentage to keep rising as more and more people purchase Smartphones.
When visitors to a nonresponsive website visit the site with a mobile device, they are forced to zoom in and out to see text better. With a responsive website design, your website pages will be easy to read and navigate regardless of the device.