On a Linux system, several desktop environments can be installed, and a user can choose which environment to use.
The default on most Linux systems is Gnome 3. However, this desktop has two drawbacks: it is quite different than other desktops, in use and looks. and it is quite heavy on the graphical hardware, making it less suitable for some of our older pcs. For new acccounts on the Sterrewacht computers, the default has been switched to Cinnamon
The graphical login screen has a “session” menu, where you can make your choice. Note that you will log in immediately after entering username and password, so make your choice before pressing enter in the password field. Your choice will be stored (in a file called .dmrc) to be used as your personal default in later sessions, unless overridden by a new menu choice.
A desktop with a traditional look, but based on the latest libraries and technologies, including 3d desktop effects, if desired.
A desktop environment that attempts to integrate the look of mobile operating systems (tablets, smart phones) into the desktop.
Starting with Fedora 21, the Gnome desktop is getting back some flexibility and might be a good choice to use, especially since it is once again possible to add back useful desktop features (menu, bottom bar with icons for running applications, etc) in stead of completely trying to emulate a tablet.
A feature rich desktop environment, ideal for users who want to be able to control all the details.
A fork of the old Gnome (version 2) desktop, with the conventional look of a desktop.
A lightweight desktop environment, suitable even for the oldest, most limited computers (or for people who want the full cpu power of their desktop for computations, in stead of eye candy). (not available on (most of) the computers of the Lorentz institute, but it can be installed if desired)
Another nice and simple, lightweigth desktop environment.
For the biggest part, it comes down to personal taste. But for a small part, some advice may be helpful.