What does the 'display' property control in CSS?

The 'display' property in CSS primarily controls the layout behavior of an element. This property determines how an element is treated in the document flow, affecting how it interacts with other elements on the page. For example, using the 'display: block;' value will make an element take up the full width available and start on a new line, while 'display: inline;' will allow it to sit alongside other elements without starting a new line.

Understanding the layout behavior facilitated by the 'display' property is crucial in web design, as it influences the overall structure of the content visualized in the browser. This includes whether elements stack vertically or horizontally, whether they take up space in the flow, and how they respond to size adjustments. Each display value serves specific purposes that can significantly impact the design and usability of a web page.