CSS styling, or Cascading Style Sheets, is a language used to describe the presentation of a web page written in HTML or XML. It allows developers to control the layout, colors, fonts, and overall appearance of a website, making it visually appealing and user-friendly. By separating content from design, CSS enables easier maintenance and updates. With CSS, styles can be applied to individual elements, groups of elements, or entire pages. This flexibility allows for responsive design, ensuring that websites look good on various devices, such as smartphones and tablets. Key concepts in CSS include selectors, properties, and values, which work together to create the desired look.