Example Concept: CSS containment is a technique that uses the "contain" property to restrict a browser's rendering work to a specific element and its subtree. By applying containment, you can prevent layout, style, or paint changes in one part of the page from affecting others, thus improving performance. For instance, "contain: layout" ensures that layout changes within the contained element do not impact the rest of the document, while "contain: paint" confines the painting process to the element itself.