"Responsive design" in web development refers to an approach that ensures websites function effectively across a wide range of devices and screen sizes. This technique utilizes flexible layouts, scalable images, and media queries to adapt content dynamically, providing an optimal viewing experience for users, whether on desktops, tablets, or smartphones. The goal of responsive design is to eliminate the need for separate mobile sites while ensuring that the user interface is accessible and visually appealing. This enhances user engagement and improves search engine rankings due to better usability.