The directory hierarchy in GNU/Linux is somewhat different to what you might have been used to in Windows. There is no C: or D: drive, instead the filesystem starts at the root node, /, then every directory (folder) is followed by another slash (/ — as opposed to a backslash on Windows). Thus, what would be C:\\Program Files\\Mozilla\\Firefox\\firefox.exe on Windows, is usually /usr/bin/firefox on GNU/Linux, and what would be C:\\Documents and Settings\\Users\\jean\\My Documents\\ on Windows is just /home/jean on GNU/Linux. Much simpler! If you want to learn a bit more, read the Filesystem Hierarchy Standard article on Wikipedia, or better yet, enter man hier in the terminal.