Glossary » progressive disclosure
the design principle that says to show overviews and hide details until the user requests more detail, and then to provide only the additional level of detail required.
This principle is often used in file systems and outlines, as with the disclosure triangle in Mac OS or the + symbol in Windows interfaces. Many dialog boxes will have a “More Options” or “Expert Options” feature to provide additional information or controls. These features allow a user to focus on the most important information first and then refine their task progressively.