If your primary use of Linux is not via an SSH connection,[2] your first experience with Linux will probably be with a graphical user interface called a desktop environment,[7] which is often used in place of the lower-level command line-based approach.
There are two particularly popular desktop environments for Linux:[8]
As explained in the next section, even if you're using a GUI, you can still access the CLI.
[6] All of these GUIs use the X Window System (also called X) as their underlying windowing system. Wikipedia has an article that surveys the window managers that are compatible with X, as well as an article about X itself.
[7] Instead of a desktop environment, the GUI in use could be a window manager, such as Fluxbox or Enlightenment. A discussion of window managers is beyond the scope of this guide, although Wikipedia has an article about them. Note that one component of a desktop environment is a window manager, as Wikipedia's article on desktop environments explains.