The UNIX File System
While the Thunar file manager does a good job at abstracting the details of the underlying file system, so the user does not need to care about them, it is sometimes useful to understand the basic concepts to get the whole picture. This section tries to give a brief introduction to the concepts of the UNIX file system, which is used today by all incarnations of UNIX, including Linux. Folders and Paths
In a UNIX file system all folders are arranged in a simple inverted tree structure descending and branching down from a single top level folder, which is called the root directory (the term directory is often used instead of folder) and displayed as File System in Thunar. This means that you can get from any folder to any other by going up the tree until you reach a common point, then down the tree through the appropriate subfolders until you reach your target.
The position of any file or folder in the tree can be described by its path. The path is the list of folders you would have to descend through to get to the target folder or file, starting from the top level folder. For example /home/luke is the subfolder luke of the subfolder home of the top level folder, and /home/luke/myfile.txt is the file myfile.txt in that subfolder. The leading / in these paths represents the top level folder.
Every user has their own folder to hold their personal files and settings. This folder is called the home directory and is displayed in Thunar as special icon with the users login name. The folder is similar to the My Files folder known from Windows. The home directories of the various users in a system are usually located below the /home folder. For example /home/luke would be the home directory of the user with the login name luke, while /home/jane would be the home directory for the user with the login name jane.
You may have already heard that everything is a file in UNIX. This is true for most objects present in UNIX systems today. In fact even devices are represented as a special files. While this may not make sense at first sight, it is one of the strengths of UNIX and its derivates, and has helped it to maintain a simple core over the years where other operating systems had to introduce new concepts for every new technology.
These are the four most important types of files in the UNIX file system. Ordinary Files
An ordinary file may contain text, a program or other data. This includes image files, audio files, office documents and video files. The term file is often used to refer to an ordinary file. Folder Files
Folders are also files in the UNIX file system. To be exact a folder is a special file, which contains a mapping of file names to file references for every file contained within this folder. Symbolic Link Files
A Symbolic link (often called a symlink) is a special file that contains a path to another file in the file system. Symbolic link files therefore do not contain any useful information themselves, but just refer to other files. Device Files
As mentioned earlier (most) devices are also accessed through the file system. These special device files are usually located in the /dev folder. For example the special file /dev/hda represents the first IDE disk on Linux.
source: verbatim from Thunar manual categorie:files