Refers to a time period in which the strong, weak, and electromagnetic forces were all unified.

The period was called the Grand Unification Epoch

It was the way the universe functioned after the Planck Epoch which started at about 10^-43 seconds after the Big Bang happened. The planck epoch is how the universe is perceived to have been before the big bang occurred. It lasted until the 10^-36 seconds after the Big Bang which in layman terms seems like a short time, unperceivable, but was extremely important.