What is the primary purpose of CSS?

The primary purpose of CSS (Cascading Style Sheets) is to style and layout web pages. CSS is a stylesheet language that allows web developers to control the presentation of HTML elements by applying different styles such as colors, fonts, spacing, and positioning. This separation of content and presentation not only enhances the visual appearance of a website but also enables easier maintenance and updates to the design without altering the underlying HTML structure.

By utilizing CSS, developers can create visually appealing layouts that are responsive and adaptable to different devices and screen sizes. This capability is crucial in modern web design, as it allows for a consistent user experience across various platforms.

In contrast, creating interactive web applications generally involves scripting languages like JavaScript rather than CSS, optimizing website performance focuses on improving load times and resource management, and ensuring web security pertains to protecting a site from vulnerabilities and attacks—all of which fall outside the primary scope of CSS.