The default settings in the Unity desktop environment move a window's control panel away from the actual window up to the top panel of the screen - this is called 'global menu'.
Since that is a major change of paradigm and might hinder your workflow if you decided to switch, here is how to reverse the settings:
Open a terminal and enter following command:
sudo apt-get autoremove appmenu-gtk appmenu-gtk3 appmenu-qt
Afterwards you need to log out or reboot your machine. To enable it again if you should change your mind, just reinstall the packages:
sudo apt-get install appmenu-gtk appmenu-gtk3 appmenu-qt