Difference between GNOME 3.x and Shell?

[nrundy]

When reading about GNOME sometimes "3" and "shell" get interchanged a lot.

Is GNOME 3.x the "underpinnings" of the new desktop environment and Shell is the UI created by GNOME for this underpinning? or is there a Gnome-3 UI and a Gnome-shell UI?

[Copper Bezel]

Shell is to Gnome 3 what Unity is to Ubuntu's flavor of Gnome 2. It's a panel alternative that manages some Gnome services and integrates with the window manager (in this case, Mutter.) Notably, just as Unity excludes Metacity, Shell excludes Compiz.

Shell is the default interface in 3.0, so they get casually lumped together in conversation. Gnome 3.0 can still use a Classic Gnome interface with a panel, but the panel itself is no longer receiving updates.