A CSS tutorial is a step-by-step guide designed to teach the fundamentals and advanced techniques of Cascading Style Sheets (CSS). It covers topics such as selecting elements, styling text, creating layouts, responsive design, animations, and transitions. CSS tutorials help beginners understand how to style web pages, while more advanced lessons delve into concepts like flexbox, grid systems, and custom properties. By following these tutorials, learners can create visually appealing and functional websites that adapt across various devices.