Here are a short bulleted list of the key points about the "parallel universes" (the "multiverse", "other universes", "alternate universes", or "many worlds"):

- It is a hypothetical group of multiple universes which together are presumed to comprise  the entirety of space, time, matter, energy, information, and the physical laws and constants that describe them.

- It has been the subject of debates in cosmology, physics, and philosophy.

- Some argue that the "parallel universes" concept lacks testability and falsifiability, and so it is a more of a philosophical notion rather than a scientific hypothesis.