Gnome Classic is a Gnome Shell feature for users who prefer the traditional desktop metaphor. It is only available on Gnome 3 systems with certain shell extensions installed.
GNOME Classic is a feature for users who prefer a more traditional desktop experience. While GNOME Classic is based on GNOME 3 technologies, it provides a number of changes to the user interface, such as the Applications and Places menus on the top bar, and a window list at the bottom of the screen.