What does the CSS box model define?

The CSS box model is a fundamental concept in web design that defines how elements are rendered on a web page. It consists of several components: content, padding, border, and margin, which together determine the size and position of an element in relation to others.

Understanding the box model is essential for effective layout and design because it allows web designers to manipulate the space around elements. For example, adjusting the margin will affect the distance between elements while modifying padding will change the space within an element itself. This understanding is crucial when styling a page to ensure a visually appealing and functional layout.

In contrast, the other options center around different aspects of web development. The structure of HTML documents pertains to the arrangement and hierarchy of HTML elements, not necessarily tied to how they are rendered visually. The organization of files in Dreamweaver relates to the software's file management features, and the process for building web applications refers to methodologies or frameworks used in development, neither of which directly informs how CSS affects layout and rendering on a webpage.