Unfortunately, one of the drawbacks of the multiple competing variants of Unix is that different versions use different filesystems, although all offer a similar basic feature set. Unlike DOS, Unix is an inherently multi-user operating system, supporting multiple users in multiple groups.
Files always belong to some user.
This type of an ordinary file is set by a number within the file, controlled by a central database on each machine. These special files are treated separately from ordinary data files. Another basic feature of Unix filesystems are links. These resemble Windows 95's shortcuts or Mac operating system's aliases, but happen at the filesystem level rather than in the user interface. A link is an entry in the filesystem that points to a file somewhere else.