By the end of 2014, the majority of internet usage will come from mobile devices, surpassing the traditional desktop computers. This means that it is extremely important to have a responsive website more than ever! A mobile ready website will provide an exceptional user experience on all devices. Usability is the primary focus of responsive design.
A traditional website is not programmed to properly appear on mobile devices. When browsed on a mobile device, the website will load the desktop version of the site. I'm sure you have experienced this in the past. The website will appear very zoomed out, and navigation and usability is difficult. Features and functions don't work properly and the load times are slow.
It is extremely likely that any potential customer will be turned off by the frustrating layout of your non-responsive website and leave your website, possibly finding your competitor's easy-to-use responsive website.
Having a separate "mobile" site is not good either. This causes you to have another URL and content, which makes managing your sites tedious and time-consuming. It is also more challenging for search engines to index and use your site, and as a result, your page rank suffers. Mobile sites do not offer the same functionality but rather strip down the site and remove features.
A responsive web design refers to how a website is created. A responsive website will automatically and properly rearrange itself for different screen dimensions. A responsive website will have fast load-times and great usability on mobile devices as well as include all of the functionality that is provided to desktop users.