Window Applets is a package that comes with two Gnome panel applets: Window Title and Window Buttons which are controls for windows that are placed on the Panel instead of the window. They provide a clever way to increase vertical screen space. See THIS screenshot to understand what this is about.
To install the Orta Window Applets theme, download it from Gnome Look, extract it, then press ALT + F2 and enter:
and copy the extracted "orta" folder to this directory.
gksu nautilus /usr/share/windowbuttons/themes/
Unfortunately, the Orta Window Applets theme only looks ok with a light Orta panel.
See also: Install Window Applets in Ubuntu from the WebUpd8 PPA.
Screenshot credits: popefalstaff