A responsive website automatically adjusts its layout and content to fit the size of the screen on which it is being viewed. This means that the same website can be used on different devices without the need for a separate version of the site for each device.
Responsive design is important because it allows a website to provide a good user experience on devices with different screen sizes and resolutions. Without responsive design, a website might be difficult to read or navigate on a small screen, or might require the user to zoom in and out to read the content.