CSS stands for Cascading Style Sheets, and it is a style sheet language used to describe the presentation of a document written in HTML or XML.
CSS allows you to control the appearance of elements such as fonts, colors, layouts, animations, and more.
CSS is one of the core technologies of the web, along with HTML and JavaScript.
History
CSS was first proposed by Håkon Wium Lie in 1994, while working at CERN with Tim Berners-Lee, the inventor of the web.
The idea was to separate the content and structure of a document from its presentation, and to enable different styles for different devices and media.
The first CSS specification was published by the W3C in 1996, and since then it has evolved through several versions and modules.