Explain the concept behind multiverse

From science fiction to science fact, there is a concept that suggests that there could be other universes besides our own, where all the choices you made in this life played out in alternate realities. The concept is known as a "parallel universe," and is a facet of the astronomical theory of the multiverse.

It is a hypothetical group of multiple universes

Explanation:

The multiverse is a hypothetical group of multiple universes including the universe in which we live. The term multiverse was coined by American philosopher William James in 1895. According to this theory these universes comprise everything that exists either in practical or hypothetically in the entirety of space, time, matter, energy, and the physical laws and constants that describe them but some scientists refuse to accept this idea.