What does a file extension indicate?

A file extension serves as an identifier that gives insight into the type of file based on its format. When a file is saved, the extension—typically the suffix after the final period in the filename—indicates what type of file it is and, often, which applications can open it. For instance, a file ending in .docx signifies a Microsoft Word document, while one ending in .jpg is recognized as an image file. This helps both users and the operating system in managing files effectively, allowing for the appropriate software to be launched for file handling.

The other options focus on aspects that are not conveyed by the file extension. File size is determined by the amount of data contained within a file and is not indicated by its extension. The date a file was created is a separate metadata attribute stored by the file system and is unrelated to the extension. User permissions are managed through access control settings specific to the operating system, not through the extension itself. Thus, the file extension is key in recognizing the file type and ensuring proper functionality within software applications.