What does the 'display' property in CSS control?

The 'display' property in CSS is primarily responsible for controlling the layout of an element within a web page. It affects how an element is rendered in terms of its visibility and the space it occupies in the flow of the document. Different values of the display property, such as 'block', 'inline', 'flex', and 'grid', determine how an element will be presented and how it interacts with other elements around it.

For instance, 'block' elements take up the full width available and start on a new line, while 'inline' elements only take up as much width as necessary and do not start on a new line. The 'flex' property enables a flexible layout structure for items within a container that can adjust according to screen size or availability of space.

Understanding the display property is crucial, as it allows web developers to define the layout structure effectively, enabling the creation of responsive design patterns that adjust elegantly across different devices and screen sizes.