According to the Wikipedia Article for Desktop Environments, here's what they stand for:
In computing, a desktop environment (DE) is an implementation of the desktop metaphor made of a bundle of programs running on top of a computer operating system that share a common graphical user interface (GUI), sometimes described as a graphical shell. The desktop environment was seen mostly on personal computers until the rise of mobile computing. Desktop GUIs help the user to easily access and edit files, while they usually do not provide access to all of the features found in the underlying operating system. Instead, the traditional command-line interface (CLI) is still used when full control over the operating system is required.
In simpler terms, a desktop environment is the Graphical User Interface (GUI) that you interact with. Icons, menus, menu bars and all the visual things come under a DE.
What Desktop Environemnts does Andronix offer?
Andronix has the support of almost all the major DE(s) that the current Linux community has. These include XFCE, LXQT, LXDE.
Desktop Environment List
Ubuntu XFCE LXDE LXQT
Debian XFCE LXDE LXQT
Kali XFCE LXDE LXQT
Manjaro XFCE LXDE LXQT
Fedora XFCE LXDE LXQT
Void XFCE LXDE LXQT
Arch XFCE LXDE
Which DE should I choose?
You can pick whichever DE you like or you are familiar with but for the most part we would recomment XFCE as a starting point for it's ease of use and customizability.