The User menu in the upper rightmost corner is identified by a bubble and the full name of the currently logged user. The bubble icon is meant to display the available or busy state in the stock IM client called Empathy.
Clicking the User menu various menu items are shown. Under the two IM status items there will be presented many others options.
My Account menu item will open the User Accounts dialog where you can configure new users and change the details of your account.
System Settings leads to the general control panel for many settings of GNOME 3.
Lock Screen will lock the current session so that the user password will be asked to unlock the session again.
Switch User will open a new X Server and will start a new login manager to allow another user to login.
Log Out item will show a confirmation dialog to close the current session and all the running programs and disconnects the user.
The Suspend menu item is meant to have a dual function: suspend the current session leaving the computer in stand-by mode or to power off the computer if the ALT key is pressed.