CSS is a language that helps describe the appearance and layout of a web page. It's like the formatting and design elements of a book that make it visually appealing and easy to read. Using CSS, web developers can define the styles and layouts of various elements on a web page, such as font size, color, background color, margins, padding, and more. This helps separate the content of a web page from its presentation, making it easier to update and maintain. CSS can be thought of as the clothing and accessories that you choose to wear to make yourself look presentable and attractive, making a web page look good and feel visually appealing.