The following article nicely explains the differences between a display manager, a window manager, and a desktop environment:
Over time, I have grown very fond of using Openbox. Here is typically how I use Openbox:
Install Ubuntu server (no desktop)
Install openbox and a system tray application.
Add "startx" to my .profile script. After I login, it automatically brings up Openbox window manager.
In this case, is it fair to say that I don't have any display manager installed?
I am just trying to understand what is it I am missing by not having a display manager. I am quite happy with the way my setup works.
Also, is it correct to say that I don't have any desktop environment either? Regards.