Linux Layers

This post is a back to the basics for understanding how Linux works.  For those of you just now migrating from Windows to Linux, this should help you understand the difference in concepts in the two operating systems.

Several years ago, Bill Gates, with the help of some other people, wrote DOS; Disk Operating System.  It was command line only, no graphics.  Then Windows came along.  It was a layer of graphic programming that "sat" on top of DOS.
Windows could not function without the bottom layer of DOS.  It was like 2 layers of a cake.  DOS on bottom, Windows on top.  Over the years,  the separation between layers has become fuzzy and the Windows part includes everything but the basic commands.  You can still run command line programs in Windows, if you know what you are doing. 
The top layer is the software, like MS Office, that interacts with the Windows program, and helps the user to be productive.

With Linux, the cake has more layers and they are distinctly separate, so far.
The bottom layer is Linux.  It will run by itself with no need for other layers.
It is command line only.  Some people build servers this way to cut down on the number of extra programs running in the background.
The next layer is the X-windows graphical interface.  It contains graphical programming to interface between a GUI (graphical user interface) desktop view and commands, and the underlying Linux operating system.
The next layer is the Desktop Window Manager.  It interacts with the X-windows system graphical interface, has the icons, mouse effects, screen savers, colors, etc.  Typically, it is KDE, Gnome, Xfce4, WindowMaker, Fluxbox, Ice, etc.      
The top layer is the software that will run on almost any Linux Desktop Window Manager.  Typically it is OpenOffice, Firefox, GIMP, etc.

I hope that helps you understand some of the basic differences in the two operating systems.

Next time, what is open source, and why it works.  

Have a good day.
Jim