If HTML is the structure of a house, then CSS is the paint and wallpaper. Cascading Style Sheets is a standard markup language that describes the formatting of markup language pages.
Before CSS, websites were kept in HTML markup, making the process more complex.
CSS is a frontend language that enables developers to separate content and visual elements for better page control and flexibility.
CSS defines formatting for HTML, XHTML, XML, SVG, and XUL.