File extensions are the suffixes after the dot in a filename (like .txt, .jpg, .exe), indicating the file's type and which program opens it. Hiding extensions means the operating system doesn't display these suffixes for files it recognizes. It simply removes this part visually for a cleaner look when browsing folders; the extension itself remains a functional part of the file and doesn't affect how it works.

The primary practical use is simplifying the view in file managers like Windows File Explorer or macOS Finder. For instance, a file named Report.docx would appear simply as Report, making lists less cluttered. This is common in everyday computing environments where users manage documents, photos, or presentations and don't need constant visual confirmation of the file type.

The key advantage is visual simplicity and reduced cognitive load. A significant limitation and security risk exist because hiding extensions can obscure dangerous file types; a malicious file named VacationPhoto.jpg.exe would appear as VacationPhoto.jpg, potentially tricking users into executing it. Therefore, many security experts recommend disabling this feature to make file types unambiguous and avoid malware risks.