What is the primary use of Cascading Style Sheets (CSS)?

The primary use of Cascading Style Sheets (CSS) is to define styles and formatting in HTML documents. CSS enables web developers to separate content from design, allowing for enhanced control over the presentation of web pages. By using CSS, developers can specify the layout, colors, fonts, spacing, alignment, and other visual aspects of HTML elements. This separation fosters a more efficient design process, as changes to the visual style can be made in one place and will automatically apply to all elements across the web pages that reference the CSS file. Furthermore, CSS supports responsive design techniques that allow websites to adjust their presentation based on device size and screen resolution, thereby improving usability and accessibility.