To show file extensions on macOS, navigate Finder preferences. File extensions are the suffixes like '.docx' or '.jpg' appearing after the dot in filenames, indicating the file type to the operating system and applications. By default, macOS hides these extensions to maintain a cleaner desktop and Finder view, though the underlying type information remains intact for files to open correctly.

For example, revealing extensions helps differentiate files like 'Report.pdf' and 'Report.docx' sharing the same base name, ensuring you open the correct one. Users editing websites might need to see '.html' versus '.css' files explicitly. Enabling extensions applies throughout macOS, affecting filenames displayed in Finder windows, desktop icons, and application save/open dialog boxes.

Showing extensions enhances precision and security by making file types unambiguous, aiding in avoiding opening malicious files disguised with misleading icons. However, users can accidentally break a file if they manually delete its extension during renaming. Future macOS updates are unlikely to change this core system preference location, reflecting Apple's balance between user-friendly defaults and providing technical control for those who need it.