V'Ger returned to Earth where its well-known encounter with the starship Enterprise took place in the year 2373. At the end of that mission, the first officer of the Enterprise, a member of the New Human movement named Willard Decker, volunteered to join with the replicated mechanical version of his Deltan lover Ilia and by extension V'Ger itself in order to form a new lifeform, a perfect synergy of Man and Machine; Creator and Creation. The New Humans were a small but growing movement on Earth consisting of Humans who had voluntarily undergone surgery to be fitted with cybernetic devices in their brains that allowed them to form a group collective consciousness when nearby others of their kind. They were derisively referred to as "Borg" by their normal Human counterparts, as an abbreviated version of "cyborg," partially because the Humans disliked their cult-like recruiting practices that indoctrinated more and more people in the "true enlightenment" of joining the New Human Collective. Following the V'Ger mission, many of the New Humans claimed to have heard Decker's final thoughts and thus as a whole set out on hundreds of ships to find their lost brethren and the promise of true perfection. They were never heard from again, and the New Human movement on Earth was never reborn.
Meanwhile, having combined the biological Decker and the mechanical Ilia (an extension of its own psyche) into a being of true perfection, V'ger decided to set out with a plan of its own. It went into the Delta Quadrant of the distant past using time travel equipment it had assimilated from countless species. It set about establishing a new Borg Collective, bent on bringing the enlightenment of the Collective consciousness and the constant seeking of absolute perfection through assimilation of new technology and biological distinctiveness to the peoples of the galaxy through the gift of assimilation. It had learned all of these things as a hybrid of its human and machine components.
The Decker Unit would become the Borg King, a timeless being who remained hidden safely at the primary Borg Unimatrix and who served as the central "Brain" of the entire Collective. Destroy him, and you destroy the Collective itself, because there is only one. The Ilia Unit would become the first Borg Queen, commanding the roving "arm" of the Collective that set out upon the galaxy with its missionary-like objective of assimilation into perfection. Over time as Borg holdings expanded, new assimilation "arms" consisting of individual Collectives were established, each with a Queen at its head. Destroy a Queen, and you would destroy that Collective, but much like the Hydra of Greek myth, a new head would eventually grow back in its place. That is why it is possible to encounter Borg with different objectives and Queens, and why when one Queen is destroyed or infected with individuality as in the case of Hugh's Collective, the other Collectives are unaffected and the original Collective can regrow with the consciousness of the Queen transferred into a new clone body.