cd means ``change directory.'' In this case, you've asked to change to the
root directory.

pwd
This verifies that you're working in the root directory.

ls
Lets you see what's in /.

cd
Typing cd with no arguments selects your home directory - /home/ yourname
- as the current working directory. Try pwd to verify this.

Before continuing, you should know that there are actually two different
kinds of filenames. Some of them begin with /, the root directory, such as
/etc/profile. These are called absolute filenames because they refer to
the same file no matter what your current directory is. The other kind of
filename is relative.

Two directory names are used only in relative filenames: . and ... The
directory . refers to the current directory, and .. is the parent
directory. These are ``shortcut'' directories. They exist in every
directory. Even the root directory has a parent directory - it's its own
parent!

So filenames that include . or .. are relative, because their meaning
depends on the current directory. If I'm in /usr/bin and type ../etc, I'm
referring to /usr/etc. If I'm in /var and type ../etc, I'm referring to
/etc. Note that a filename without the root directory at the front
implicitly has ./ at the front. So you can type local/bin, or ./local/bin