A responsive website adapts to different screen sizes and devices like mobile phones and tablets. It has content that flows based on the size of the screen or browser viewing it. Key benefits of responsive design include a consolidated user experience across devices, improved browsing and higher conversion rates, lower bounce rates, and better search engine optimization as search engines favor mobile-friendly sites. The majority of internet users now access the web on smartphones, and responsive design helps ensure they can easily view a site from any device.