WordPress Design with All Your Visitors in MindCreating custom WordPress sites that look great - on every device.
Responsive design is an HTML and CSS markup technique of designing to automatically scale for optimum display on different devices and screen sizes.
To explain this a little more, imagine your WordPress site on your desktop. It has a great deal of detail and the different pieces (menu, main content, footer) are spread throughout the page.
The same site on a tablet, the design is slightly different, factoring in the new, smaller proportions. The most obvious change is when you open the same site on a mobile device, and the components are stacked and the layout and display is much more minimal.