The Borg Collective is the term used to refer to the collective consciousness of the Borg. It is considered the governing body of the Borg, though there are no true leaders within the Collective. The Borg Queen serves in some form of leadership role, but the exact role is unknown.
The majority of the Collective was primarily located in the Delta Quadrant. The actions of an alternate timeline iteration of Kathryn Janeway that took place during the USS Voyager's return to the Alpha Quadrant caused severe damage to the Collective and the Unicomplex, considered to be the "capital" of the Collective.
In Remington continuity, Admiral Janeway's actions were believed to have completely destroyed the Collective. It is not known what happened to the individual drones and ships after the collective consciousness was terminated.