The @media CSS at-rule can be used to apply part of a style sheet based on the result of one or more media queries. With it, you specify a media query and a block of CSS to apply to the document if and only if the media query matches the device on which the content is being used.
The @media rule is used in media queries to apply different styles for different media types/devices. Media queries can be used to check many things, such as: width and height of the viewport. width and height of the device.