What’s one of those then? The technical answer is that it’s a design that responds to the display resolution of the browser and adapts the layout of the content accordingly.
What does that mean in English? In short it means the site layout is optimised for the screen. The site layout will vary according to whether you’re viewing on the desktop, a tablet or a phone. In the case of this site it means that the links to recent blog posts, categories and archive move below the main content on a narrow display but are shown to the right on a desktop.
The first picture shows the site on a desktop, the second on a phone. Contrast that with a screenshot of one of my other sites on a phone. The theme is not responsive so you get a tiny view and have to pinch and zoom to read the content.
Before responsive web design took off displaying differently on small screens was usually done by maintaining a separate version of the site for mobile devices and then attempting to guess what type of device was accessing the site.
The advantage of doing it this way is that you can preview the site as it would appear on different devices simply by resizing the browser window.
The downside is that you really, really need to know your way around css, which is why I started from a pre-built theme.
If I can really get my head around it I’ll be converting my existing sites to responsive design, but it’s a scary amount of work…in Web Design