CSS, or Cascading Style Sheets, is a stylesheet language used to describe the look and formatting of a document written in a markup language. It is most commonly used to style web pages written in HTML, but can be used with any kind of XML document, including SVG and XHTML.
CSS is used to define the layout and design of a document, including the font, color, and size of text, the placement of elements on the page, and the styling of elements such as buttons and links. It allows developers to separate the content of a document from its presentation, making it easier to maintain and update the design of a website without changing the underlying HTML.
CSS offers a wide range of features, including the ability to apply different styles to different devices or screen sizes, to create animations and transitions, and to define the behavior of elements when they are hovered over or clicked on. It also enables developers to create responsive designs that automatically adjust to the size of the user's screen, providing an optimal viewing experience on any device.
Overall, CSS is an essential tool for web developers, allowing them to create visually appealing and user-friendly websites.