You will create directories to store files in. Directories allow you to group files together by form or function. Think of them like drawers in a filing cabinet, or even file folders. This directory structure begins at your personal directory. This path varies, depending on how it's set up at different internet providers.
Paths refer to file location and directory structure.
The directories csci121 and mail do not have any subdirectories. In UNIX file names and commands are case sensitive. If you look for a file named communities- bibl and if it's really spelled Communities. Bibl, then you won't find it. You can often break out of commands by pressing Ctrl-c.