A responsive website adapts to fit the size of the viewing window. It should work equally well whether it is displayed on a large-screen desktop monitor or a smart-phone.
When you visit a responsive web page, the server sends your browser the complete content for the entire page, as well as styles, or display instructions, for all types and sizes of device. Your browser then uses the style information to determine what to display, and how to display it.
The styles may tell your browser to re-arrange elements on the page, or to discard some elements entirely. Pictures and graphics may be scaled down, type sizes may be changed, and navigation menus may be displayed differently.
On the surface, this sounds like a great idea. The webmaster need only manage one version of each page, and it will be automatically formatted to fit any device.
However, there is a cost! Responsive sites are often made up of many large files. As a result, it can take a long time for a responsive page to download, especially if the user has a slow data connection (which often happens with phones). If the connection is really bad, the page might not display at all.
Also, it's important to realize that desktop users and mobile users are looking for different things. Someone who visits a business site using a smartphone may want to know your business location, or hours of operation; he may want to see a restaurant menu. However, smartphone users are usually not interested in reading large amounts of text, or visiting lots of pages.
Rather than building a responsive website, it often makes sense to build a small number of pages specifically for small-format devices and phones. The pages should contain just the information that mobile device users are likely to want, and they should be made up of small files built to load very fast.
Your server can be configured to automatically send the simplified pages to mobile device users, resulting in a better experience for your customers.
Note that this website is built using a lightweight, responsive commercial theme from Mojo Marketplace.