There is only one directory tree. It starts witha root directory from which
everything else branches off. The name of the root directory is /.

Under it are many subdirectories, most of which are only of interest to the
advanced user. The one everyone uses is their home directory where are
personal data and files are found. It is called /home and in that folder
are subdirectories for each user. At a minimum there is one with your
username, /home/user (you don't see "user", just your login name) and one
for the administrator or root user, /home/root. Each is private to that
user and can only be used by him/her.

Each user's home directory contains folders such as documents
(/home/user/documents), downloads, music, videos etc, as well as a lot of
hidden configuration files. The default permissions give each user
exclusive rights to their home directory, unless they are the root user,
who can go anywhere and do everything. You are not root when you log in.

It's a very simple and logical layout compared to that other well known
operating system that starts with "W". All Linux file managers show the
same "tree" structure and the names of the important directories never
change. As you gain more experience with Linux you will come to appreciate
this but for now, just remember that unless you are the administrator,
root, you only have access to your own area, your home directory. This is
for your own protection and that of all the other users since Linux is a
multi-user operating system.