Let's Begin With Linux File Permissions
Even if you're on a distro designed for a single user who works in a Graphical User Interface (GUI) as root all of the time such as Puppy, you can still exit to a prompt and practice these commands. Simply proceed as though you were going to shut down but choose the option to exit to a prompt which will take you automatically to a command line as root where you can create fictitious users and practice files. If you're on a system like Fedora, Debian, or Mandriva, your experience will be a little different and closer to the work of a Linux or UNIX administrator in the real world. Every file has an owner, the user who created it is the initial owner (ownership can be changed). It also carries Linux permissions for being read, edited (written to), or executed by the owner, a group of users, and others. A user who is neither the owner nor a member of the group to which the owner belongs, falls into the "others" category. These three categories cover everyone, even guests on the system.
Remember that root, commonly referred to as the super user, has all permissions on all files, directories, and programs all of the time; root is the master user. Now is a good time to open a terminal; it could be called a console on your system, become root (or open a terminal as root) and create a practice file in whatever directory you want. You can use the simple "touch" command to create the file. If you want to create a directory, you can use "mkdir." Omit the quote marks and type only the command between them. You can then immediately find out the default Linux permissions by typing "ls -l" plus the name of the file. To get the report on a directory, type "ls -l" and press enter. In the screen shot below you can see I've created a practice file called "test.txt," you can also see the Linux permissions report I generated for it. Likewise, I created a directory called "Practice" on which I also generated a Linux permissions report.