The Halo Array is the seven halo rings. The Halo Array have many names, such as the Sacred Rings by the Covenant, Shield Worlds by the Forerunners and Installations by the AI Monitors that run it. These rings were created by the Forerunners as a last resort weapon to combat The Flood. The ring didn't kill the Flood but it killed there food supply, this was told in Cortana's Speech in Halo: Combat Evolved. The speech is as following. "Halo doesn't kill Flood. It kills their food. Humans, Covenant, whatever. We're all equally edible. The only way to stop the Flood is to starve them to death. And that's exactly what Halo is designed to do: wipe the galaxy clean of sentient life."