#  / - the root directory. It is the parent of all other directories. Everything starts here. There is nothing above the root directory.
# /bin - contains executable program files
# /etc - contains configuration files
# /dev - contains special device files to access hardware devices
# /lib - contains libraries needed by programs in /bin
# /tmp - contains temporary files
# /proc - contains files providing information about the system
# /usr - contains a subhierarchy of directories containing things that are interesting to users of the system, but are not vital for system operation

    * /usr/bin - contains more executable programs
    * /usr/lib - contains more libraries needed by more executable programs 

# /var - contains files that change often.