What's the difference between desktop managers and display managers? [duplicate]

Solution 1:

Display manager

Is a graphical user interface that is displayed at the end of the boot process in place of the default shell.

There are various implementations of display managers:

GDM — Gnome display manager.
LightDM — Cross-desktop display manager.
LXDM — Lxde display manager. 
SDDM — QML-based display manager and successor to KDE4's kdm.
SLiM — Lightweight graphical login solution.
XDM — X display manager with support for XDMCP

Desktop environment

Is an implementation of the desktop metaphor made of a bundle of programs running on top of a computer operating system, which share a common graphical user interface.

A desktop environment typically consists of icons, windows, toolbars, folders, wallpapers and desktop widgets, might also provide drag and drop functionality and other features that make the desktop metaphor more complete.

There are various implementations of desktop environments:

Unity is the default desktop for Ubuntu, and is one of the major desktop environments.
Gnome is other of the major desktop environments.
KDE is other of the major desktop environments.
Xfce is a much lighter desktop environment.
LXDE is arguably the lightest option available for a desktop environment.
Cinnamon is another alternative to Gnome.
MATE is a continuation of the Gnome 2 codebase.
Budgie is the default desktop of Solus Operating System.
Moksha is a continuation of the Enlightenment 17 desktop.
Enlightenment started as a project to build a desktop environment.
Pantheon is the project developed by the elementaryOS team.
Trinity is a continuation of the KDE 3 series. 

A desktop environment can be broken up into several components that function independently and interact with one another to provide the look and feel and functionality of the desktop environment.

A fundamental part of a desktop environment is the window manager.

A window manager creates a certain way for application windows to present themselves to the user. It manages the various application windows, keeping track of which ones are open and providing features to switch between them.

Another important element of a desktop environment is the file manager. This application manages files/ folders and presents them in a way that the user finds convenient. It provides file operations like viewing, copying or moving, changing permissions and deleting.

Desktop environments usually provide utilities to set wallpapers and screensavers, display icons on the desktop, and perform some administrative tasks.

They may optionally include word processors, CD/DVD writing applications, web browsers and e-mail clients.

The X Window System is usually started as an X session which is the combination of an X server and connecting X clients. For the normal desktop system, both of them are executed on a workstation.

Xorg is the most popular display server among Linux users. Its ubiquity has led to making it an ever-present requisite for GUI applications, resulting in massive adoption from most distributions.

The X Window System is a windowing system for bitmap displays, common on UNIX-like computer operating systems.

X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting with a mouse and keyboard.

X does not mandate the user interface – this is handled by individual programs. As such, the visual styling of X-based environments varies greatly; different programs may present radically different interfaces.