File – a file is set of data items, such as this document, with a name and an entry in a nested file and folder structure. This starts from a so-called root directory which contains entries for sub-directories or folders or files. A folder can, in turn, contain sub-folders or files and so on with a file-folder structure capable of having 100s of levels and billions of files. A file-folder structure is implemented on desktop and notebook computers and can also be implemented on servers. A shared storage device holding files is called a filer or NAS, Network-Attached Storage system, and it is accessed using the Unix Network File System (NFS) or Windows Server Message Block (SMB) protocol. CIFS (Common Internet File System) is an SMB dialect.

A Mac file-folder listing. The blue icons are folders.