Don't know if this question is on topic; I posted it here just because I've heard about these differences only in the Unix/Linux world.So, as the title, what is the difference between graphical environment, user interface, graphical shell and a windowing system? How they cooperate and how are they built on top of each other?For example, from en.wikipedia, I've read that Unity (user interface)  Unity is a graphical shell for the GNOME desktop environmentorGNOME ShellGNOME Shell is the graphical shell of the GNOME desktop environment
what is the difference between graphical environment, user interface, graphical shell and a windowing system?
desktop environment;gnome shell;user interface
Basically, without going too much into detail:The User Interface (UI) is a generic term for the space where interactions between user and computer occur.  Mainly, you're talking here about a Graphical User Interfaces (GUI).The desktop environment is a GUI which is an implementation of the desktop metaphor and allows users to interact with an operating system.  GNOME and KDE are examples of Linux desktop environments.The graphical shell is the core of a specific desktop environment and allows the user to do basic tasks such as launching a program or searching for files. 