Why the change
The interface you see when you have no applications open is a called a desktop "shell". This includes how you find and launch applications, switch between applications and find information provided by applications (notifications).
Back in 2011 Ubuntu switched from the desktop shell provided by GNOME to it's own desktop shell named Unity. This is the user interface many Ubuntu users today are accustomed to. Canonical, the sponsor of Ubuntu, has decided to collaborate with the GNOME project rather than continue development of Unity. As of Ubuntu 17.10, the Ubuntu Desktop's default desktop shell is a slightly modified GNOME 3 experience.
How to use the vanilla GNOME Shell in Ubuntu
As mentioned above, Ubuntu is providing a modified GNOME user experience. Of course it's possible to use default GNOME shell on Ubuntu. Simply install the gnome-session package via apt or gnome-software, logout and choose the "GNOME" session from the login manager. To switch back to the Ubuntu experience, logout and choose the "Ubuntu" session from the login manager. That simple!
What isn't changing
Apps! For the most part, the default apps shipped as part of the Ubuntu Desktop will remain the same.
What is changing
Scopes -> Search providers
- No more HUD, global menu, locally integrated menu
- Messaging menu
- notifications in notification tray
- Window management keyboard shortcuts
Workspaces & multi-monitors
- Window controls moved to the right
- Other minor changes:
- Online Accounts
- Login greeter
How can I get involved
- GNOME engagement team
- Ubuntu community team