What does the 'overflow' property control in CSS?

The 'overflow' property in CSS plays a crucial role in controlling the behavior of content that exceeds the boundaries of an element's box. When content is larger than the container, the 'overflow' property determines how this excess content is handled.

Setting the property can lead to different display scenarios: it can hide overflowed content, scroll through it, or allow it to be visible outside of its designated area. For example, using the value 'hidden' will render any overflowing content invisible, while 'scroll' will provide a scrollbar to allow users to navigate through the extra content. This functionality is fundamental for maintaining a clean layout and ensuring that content does not disrupt the design of a webpage.

Other options address different CSS functionalities, with size adjustment pertaining to dimensions of elements, layering referring to the z-index and stacking order, and text wrapping relating to how textual content fits within its containing box, none of which are directly related to managing how overflowed content is displayed.