Media queries are a web design technique that makes it possible to customise the presentation and design of websites on different devices and screen sizes. Media queries can be used to apply specific CSS styles to certain devices, screen sizes or resolutions.

Media queries use queries in the CSS file to determine what device or screen size the user is using. Different styles can then be applied to this specific size or resolution to ensure that the website is displayed optimally.

Media queries are particularly important for responsive web design as they allow websites to look and function well on different devices and screen sizes. With media queries, the layout of the website can look different on mobile devices than on desktop computers to ensure an optimal user experience.

Overall, media queries are an important technique in web design that can help to ensure that websites are displayed optimally on different devices and screen sizes. By using media queries, websites can be designed flexibly and attractively to ensure a good user experience.