Creator was the designation given by V'Ger to the entity that had created it. V'Ger did not know what the Creator was, but believed that it was an artificial lifeform, like itself. The goal of V'Ger's journey was to find the Creator, to join with it and become one with the Creator. After Spock had mind melded with V'Ger, he commented: "It only knows that it needs... But like so many of us, it does not know what."
In the 2270s, when V'Ger arrived to "the Creator's planet", Earth, the Creator did not respond to it. V'Ger initially thought that the Human "infestation" of Earth was somehow interfering with the Creator. It was then discovered that V'Ger was in fact the ancient Earth probe Voyager 6, and that 20th century Humans were its creators. V'Ger's ultimate goal, to find the Creator and merge with it was achieved when Willard Decker chose to sacrifice himself to save Earth and merged with V'Ger. (Star Trek: The Motion Picture)