A command interface was the process by which the Borg Queen was able to access and control the various aspects of the Collective.
In 2375, the Queen utilized this interface to adapt to Seven of Nine's attempt to shut down a dispersal field the Queen was using to prevent the crew of the USS Voyager from obtaining a transporter lock on Seven and Captain Janeway, who were trapped in the Queen's chamber aboard the Unicomplex. Janeway was able to disrupt the Queen's interface, however, by destroying the Queen's power node, allowing herself and Seven to escape. (VOY: "Dark Frontier")