CSS stands for Cascading Style Sheets. It is a stylesheet language used to describe the presentation of a document written in a markup language. A CSS rule-set consists of a selector and a declaration block.
The selector points to the HTML element you want to style. The declaration block contains one or more declarations separated by semicolons. Each declaration includes a CSS property name and a value, separated by a colon.
CSS is used to style all HTML tags, including the document's body, headings, paragraphs, and other pieces of text. CSS can also be used to style the display of table elements, grid elements, and images.