The directory structure in Linux is way different then in Windows and i really like it!. You can see the directory structure in Linux as a tree (remember the tree view from windows apps?).
The "root directory" or "/" is the toplevel directory as explained above me, when you think of a tree then this are his "roots". All other folders will be like leaves on that directory. You can check out your own root directory by typing: "cd /". Change Dir /.
Now you might be wondering where your "My Documents" folders are kept. Well for every user there is a folder in "/home". There you have it, there's the root directory again, and as you can see the folder home is a directory in the root folder. Now every user has a folder in "/home", let's say your username is "test" then your home directory would be "/home/test". And only you have access to it.
"/opt" contains the information about your computer like the cpu speed and more.
"/etc" contains most of the configuration files.
"/bin" contains the programs which are used by the base linux system like the command "cd" or "ls", "dir" etc.
"/sbin" sbin stands for secure bin. It's a directory with programs that only root can use. This directory, just like /bin contains programs that the base linux system uses.
"/usr/bin" contains optional programs like text editors and all other programs.
"/usr/sbin" contains optional programs which only the root user can use.
Note: The root user is like the Administrator account on windows systems. The root user is always available on every linux system, although there are exceptions but, normally there is a root user.
Unlike windows, linux doesn't have one graphical shell which is "it". No, linux let's the user chose which graphical desktop environment he wishes to use, and if you like then you can program your own to fit your needs. Most used environments are: Gnome, KDE, XFCE, Enlightenment, Fuxbox and a lot more.
You can install programs by using your package manager, i don't know which linux distribution you are using but almost every linux 'distro' comes with an package manager through which you can install all available applications. All those applications are completely free and open-source. So you can modify it (if the license allows it) or help that team improving it. So you see, it is all built on a large and open community.
If you don't know what a command can do then type:
And replace <command> with your command which you want to know more about. Also most commands support the --help or -h option.
Now would you like to tell us if you are in a graphical environment? Eg. Gnome, KDE ?
Btw. if you switched to TTY1 (Ctrl+alt+F1) then you can switch back to graphical mode by doing the same but pressing F7 (Ctrl+alt+F7).
You're welcome for more questions!