In Linux you generally have two types of desktops: DEs, which are full featured (KDE, GNOME, Cosmic, Cinnamon, etc.), and window managers. Window managers do only what they say on the tin, if you used one with genuinely no config (they usually have minor defaults to prevent this) you would be completely soft-locked: an empty desktop just a cursor to play with, no way to launch apps, nothing.

They have a special layer into which apps can spawn windows that typically do things like adding a launcher, or an app switcher, notifications, or whatever else you want. It's the unix philosophy brought to the UI domain. Usually you have a separate app for each, but DMS brings in a full suite: allowing you to use the window manager without having to spend hours ricing your system.