Buddha is originally defined as a person who decides to become spiritually awakened out of compassion for the suffering in the world.
However, within certain Mahayana sects, a Buddha is also defined as the incarnation of a person who becomes a Buddhist monk of a spiritually high rank. He then vows to be reborn as a Buddha by making a series of vows to realize the Buddha world in which he is reborn.
In his meditations, he visualizes this Buddha world in detail. Then he reports it to his fellow Buddhists to help inspire them to reach the same spiritually high rank.
But is a Buddha a god? Not in the sense of a Creator since a Buddha is reborn in his Buddha world.
So is the Buddhist monk who realizes this Buddha world a god? Not at all, for the karma of his vow to be reborn as a Buddha resulted in that world being "created."
Yet that monk is still a man, who was born, sought to relieve suffering by becoming a monk, and reached parinirvana on his death.
Therefore a Buddha is not a god.
In the case of the Pure Land of Bliss, the Buddha reborn in it is Amida Buddha. In his previous incarnation, possibly in another system of worlds, he was the monk Dharmakara. Formerly a king, he learned of the Buddhist teachings through the Buddha Lovesvararaja and renounced his throne.
Resolving to become a Buddha, he came into the possession of a Buddha world, a world existing in the primordial universe outside of ordinary space time through the merit of his meditation practice, a world having many perfections.
Through his 48 vows, his resolutions were expressed. These vows described the type of Buddha world
After many rebirths accumulating great merit, Amida achieved buddhahood and still dwells in the Buddha world called the "Pure Land of Bliss."
Suppose for a moment though, that Buddha worlds, Pure Lands and even other systems of worlds, are a part of a specific multiverse. Let's call that multiverse Buddhadharma.
In Buddhadharma, the Indian gods also come to visit a Buddha world of their choice. Once they appear there, the gods listen as the Buddha who resides there instructs the bodhisattvas on their mission before each one of them is reborn in anther part of the Buddhist multiverse. These bodhisattvas are Buddhist laymen, monks and nuns who aspired to be reborn in that Buddha world, and have yet to achieve Buddhahood.
As well, there are also many pesky demons which that Buddha has met in previous incarnations who wait outside the gate to this Buddha world, hoping to hear the Buddha as he instructs his disciples.
Furthermore, let's also imagine that the three worlds of existence (formless, form, and desire) of Buddhist cosmology also exist in the Buddhist multiverse.
Now, where do you suppose that multiverse exists? Why, in our imagination! Perhaps in our dreams, were we to aspire to be Buddhist, and in our lives, were we to dedicate ourselves to the Buddha.
Yet, I am of the opinion that the Buddhist multiverse exists in any sentient being's mind who learns the Buddha's teachings.