The creation of the Universe is mentioned and described many times throughout the Belgariad, Malloreon and the prequels, Belgarath the Sorcerer and Polgara the Sorceress. The Universe's origins and mythos in the novels is quite unique, and it is almost a character of its own, albeit a vague one.
The Universe came to being on its own, with a Purpose, and something went wrong in the earliest moments, splitting the future into two Possibilities. One possibility led to the continuation of life and existence, and the other to its utter destruction. These two Possibilities became spiritual entities of their own; the Prophecies of Light and Dark, anthropomorphised and aware with the power to influence people and events.
After the Universe formed, it gave birth to the Gods. First, the Father of the Gods, UL. UL in turn created his Sons, Aldur Belar, Mara, Chaldon, Nedra, Issa and their wicked brother, Torak. All together, the Gods created the planet on which the story takes place for the purpose of resolving the rift created by the mistake in the earliest moments of formation. UL, Aldur and to a lesser extent, Belar all serve the Prophecy of Light. Mara, Chaldon and Nedra tend toward neutrality, serving either side as they please, although they clearly despise their brother Torak, and lean toward the Light. Issa more often seems to serve the Dark, although sevres the Light in the end. Torak, is the God-manifestation of the Mistake and exclusively serves the Prophecy of Dark.
The Gods have limited power, and can not override the will of their Creator, the Universe, who is their Mother. While they are extremely powerful, they are not fully omniscient nor omnipotent. There are many things and events they can not see, and may not always reveal everything they do see, often being confined to revealing it as riddles or obscure prophecies. While they have great power, none, even altogether, can fix the Mistake, alter certain events (Mara can not seem to recreate his people), nor may they unmake that which has been made. The Gods are not perfect, but are beings with personality flaws, and capable of making mistakes (The dragons are a perfect example of this) Also, it should be noted that they are not completely immortal or invulnerable. As was proven through Torak, they can be hurt, and once they are can not heal, and they can indeed be destroyed. The Gods are instruments of the Universe rather than rulers of it.
The Universe and its Prophecies work through not just the Gods, but through sorcerers, people, animals, and events. Those that willingly serve the Purpose of the Universe are rewarded for their service in that the Universe makes their service pleasurable. Those that do not serve their Purpose are tormented, punished and often destroyed.
The actual Purpose of the Universe itself is never clearly defined or explained, and often left up to the reader to infer for his or her self. It could be said, after reading the entire series, that the Purpose of it is to simply exist and to continue indefinitely. But that is a matter of opinion and must be left to the individual reader.