What is my linux laptop desktop environment?

I had purchased brand new laptop from System76. It is Ubuntu 18.04 LTS (64-bit).

From the desktop, I click on ‘help’ icon. ‘Ubuntu Desktop Guide’ page pops up. The first topic is “Getting Started with GNOME”. Does this mean GNOME is my desktop environment?
I’m bit confused because when I type echo $DESKTOP_SESSION from command prompt, it returns ‘ubuntu’. Why is this command returning my Linux distribution? Shouldn’t it return my desktop environment?

Regards,

Hi jani,
perhaps this might help:


Greetings.
Rosika

18.04 uses Gnome as desktop environment by default ( pre-built ).

Mine is Mate.
And I wish all distros had the same version of Mate.