The Universe is defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them. However, the term "universe" may be used in slightly different contextual senses, denoting such concepts as the cosmos, the world or Nature.
It is possible to conceive of disconnected space-times, each existing but unable to interact with one another. An easily visualized metaphor is a group of separate soap bubbles, in which observers living on one soap bubble cannot interact with those on other soap bubbles, even in principle. According to one common terminology, each "soap bubble" of space-time is denoted as a universe, whereas our particular space-time is denoted as the Universe, just as we call our moon the Moon. The entire collection of these separate space-times is denoted as the multiverse. In principle, the other unconnected universes may have different dimensionalities and topologies of space-time, different forms of matter and energy, and different physical laws and physical constants, although such possibilities are currently speculative.

Many cultures have stories describing the origin of the world, which may be roughly grouped into common types. In one type of story, the world is born from a world egg; such stories include the Finnish epic poem Kalevala, the Chinese story of Pangu or the Indian Brahmanda Purana. In related stories, the creation is caused by a single god emanating or producing something by themselves, as in Tibetan Buddhism concept of Adi-Buddha, the ancient Greek story of Gaia (Mother Earth), the Aztec goddess Coatlicue or the ancient Egyptian god Atum. In another type of story, the world is created from the union of male and female deities, as in the Maori story of Rangi and Papa. In other stories, the universe is created by crafting it from pre-existing materials, such as the corpse of a dead god - as from Tiamat in the Babylonian epic Enuma Elish or from the giant Ymir in Norse mythology or from chaotic materials, as in Izanagi and Izanami in Japanese mythology. In another type of story, the world is created by the command of a divinity, as in the ancient Egyptian story of Ptah or the Biblical account in Genesis. In other stories, the universe emanates from fundamental principles, such as Brahman and Prakrti, or the yin and yang of the Tao.