A desktop environment is a collection of software running on top of an operating system that makes up the desktop Graphical User Interface. It usually includes everything from how the windows look and feel, to the style of the icons, files, folders, and the mouse pointers. A desktop environment also dictates what file manager to use, default text editor, image viewer, wallpapers, and the interface used to log in and log out of the local system.
On Microsoft Windows and macOS X, the desktop environment is part of the operating system itself. On operating systems such as Linux, the desktop environment is usually a modular component that can be changed and reconfigured more easily.