Cascading Style Sheets, or CSS, is a fundamental programming language used for web design and stylizing the presentation of HTML-based pages. It refers to a set of instructions for how different parts of a web page must be displayed for users. Contrary to HTML, which defines the structure of a web page, including paragraphs, headlines, links, and images, CSS focuses on defining the style of how these elements must loop, including colors, layouts, fonts, and other aspects.
With the help of CSS, web designers can build multiple pages using the same formatting. It also separates presentation coding from the content, enhancing accessibility and reducing coding time. This feature allows designers to render multiple versions of a single page for alternate formats.