A responsive website is one that changes based on the screen size of the device. It has dynamic content that changes, optimized images, correct spacing based on device, and is reliant on mobile operating systems for functionality. With a responsive design, texts and images change from a three-column layout to one that fits your device’s screen perfectly. If you’re on a website on desktop and want to see if it’s responsive, simply shrink the window and observe whether or not the display changes to match the window size. Responsive websites react with the user in mind, and enhance usability no matter what the device is.
Simply put, a mobile friendly site functions the exact same way regardless of the device. In other words, mobile-friendly designs do not change based on the device being used. Nothing changes in the functionality other than the scale of the site. Many great features of the website, like navigation drop-downs, are limited, as they can be difficult to use on mobile.