The DC Universe refers to a unified world view composed of the comics under American DC Comics, including the comic characters (Superman, Batman, Wonder Woman, The Flash, Green Lantern Hero, Sea King, etc.), the cosmos, divine spirits (God, New Gods, etc.), historical directions, physical laws, and more.
The DC Universe once included countless parallel universes, but after the 1986 "Crisis on Infinite Earths," it was controlled to just one. After the 2005 "Infinite Crisis," DC again controlled the parallel universes within the DC Universe to 52. In the 2015 "Multiverse Furnace" and "Action Comics," it is mentioned that there are other universes beyond the 52 parallel universes.
Although DC canceled the parallel world concept between 1986 and 2005, they created the concepts of the Super-Time Stream and Pocket Universe to replace the Multiverse concept.
Strictly speaking, the film universe, television universe, game universe, and animation universe are also considered part of the DC Universe, but DC has not specifically numbered these derivative universes.
In the 1950s, DC Comics acquired many comic companies (for example, Captain Marvel was not originally part of DC Comics). To prevent logical conflicts in the setting of different series of comics, DC Comics introduced the concept of Parallel Universes. Another reason was to allow heroes from the 1940s to meet those from the 1960s.
However, over time, as various parallel universes increased in number, comic characters and their settings became chaotic. In 1986, DC Comics used a major event: the Crisis on Infinite Earths, to revise the entire DC Universe setup. Parallel worlds were eliminated, and any remaining heroes from different worlds stayed in the single universe.
Although DC canceled the parallel world concept between 1986 and 2005, shortly afterward, they created the concepts of the Super-Time Stream and Pocket Universe to replace the Multiverse concept.
Afterwards, DC Comics has made several modifications to the DC Universe. Among the more important were the "Infinite Crisis," in which the history and continuity of the Main World were revised. Afterward, the major event "Flashpoint" was released, resulting in the creation of 52 parallel universes once again. The universe where the mainstream comics are set has been named New Earth or Earth-0. In recent years' N52's "Rebirth," most heroes' issue numbers were reset to zero, and some characters' origin stories were adjusted.
In the 2015 "Multiverse Furnace" and "Action Comics," it is mentioned that there are other universes beyond the 52 parallel universes.
DC Comics' main competitor, Marvel Comics, also adopts a similar parallel universe worldview.