Responsive web design is an approach to web development that ensures websites function well on a variety of devices, including smartphones, tablets, and desktop computers. It uses flexible layouts, images, and CSS media queries to adapt the website's appearance based on the screen size and resolution. This design technique improves user experience by providing a consistent look and feel across different platforms. By automatically adjusting elements like text size and navigation menus, responsive web design helps maintain usability and accessibility, making it easier for users to interact with the content regardless of their device.