After the login in GNOME 3 a lot of applications will be automatically started in order to execute many invisible tasks like to notify you of incoming alarms in the calendar or to unlock your keyring containing your saved and encrypted passwords.
There’s a tool in GNOME 3 which allows to add, modify and remove the autostart entries and you can run it by executing from a terminal or from the ALT+F2 dialog the command:
While it’s surely the most important part of the GNOME Shell I left it at the last to give it more attention as it needs. I’m obviously talking about the Activities button, located in the upper left corner of the panel.
You can click upon it but you can also simply move the mouse pointer in the upper left corner of the screen to make it react as it was effectively pressed. In such case, a light blue animation (called ripple) is shown to help the user understand why the Activities screen was shown.
With the default keyboard configuration, the left Win key also works like to press the Activities button.