Alternatively referred to as file management and sometimes abbreviated as FS, a file system is a method of organizing and retrieving files from a storage medium, such as a hard drive. File systems usually consist of files separated into groups called directories. Directories can contain files or additional directories. Today, the most commonly used file system with Windows is NTFS.
Without a file management, all files would have no organization and it would be impossible for a file with the same name to exist. Files are most often managed in a hierarchy, which allows you to view files in the current directory and then navigate into any subdirectories.