To change directories use the cd directory name command. People used to using PC's should note that is a forward, and not a backward slash. To return to your home directory, just enter cd on its own. For those that have used DOS before, UNIX directory structure shouldn't be too difficult, as it uses a tree structure to organise files and directories in a similar manner. For those that are used to Macs, think of directories as being the same as folders.
Any directory can contain files, or other directories.
A directory can contain files, or other directories. Note that the fiction directories in the hardback and paperback directories are completely separate entities and are not related in any way. From the paperback directory, to get to the hardback directory, we have two options. If you don't understand this all completely, just have a play with it and see what happens. You can always find out where you are in the directory structure by typing the pwd command, and you can always get back to your home directory by typing cd on it's own.