The parallel universe and the main universe in American comics were important concepts that distinguished them from the real world. Parallel universes referred to universes that were different from the main universe. Each universe had its own unique storyline and characters. These universes are often described as "coexisting", which means that they exist in the same physical world but have different histories and events. The main universe was one of the most famous concepts in American comics. It was the only reality in all parallel universes. The main universe was often called the Marvel Universe because it was one of the main creative areas of Marvel Comics. In the main universe, superheroes, villains, and supernatural phenomena were all real and had their own fates and storylines. The difference between parallel universes and the main universe was that they existed in different physical worlds and had their own unique storylines and characters. These universes were often called "parallel universes" because they coexisted with the main universe but had different histories and events. Although the existence of parallel universes is an important concept in American comics, they are usually fictional and only exist in comics.