In 1934, the company that would become DC Comics was known only as National Allied Publications, mostly known for producing the tabloid New Fun: The Big Comic Magazine. National’s original comic book publications were essentially newspaper comic strips published in anthology form. The comics ran the gamut of genres from comedic “funnies,” Westerns, adventure stories, and eventually other anthology magazines, including Adventure Comics and, in 1937, planned to launch the new (and notably-initialed) Detective Comics.Planned to features fictional comic detectives like Slam Bradley another hero of Superman creators Jerry Siegel and Joe Shuster
With Batman and Superman now providing two sales hits, Donenfeld merged his two publishing brands (National Allied and Detective Comics) with All-American, founding National Comics (later National Periodical Publications). Pehaps due to this frequent consolidation and rebranding, the early 1940s saw published comics feature seals on their covers, reading: “A DC Publication,” “A Superman DC Publication” and “Superman DC National Comics.” Naturally the "DC” stood for Detective Comics as the incorporated publishing company, but with the other wording in the seal, the name had to be shortened. Creating their own solution, readers soon began referring to the publisher's books as “DC comics.”
But the heart of the matter, and the one that keeps characters like Batman and Superman from meeting up with Spider-Man and Wolverine (and least regularly), is that Marvel and DC are separate publishers, owned by different parent companies.Simply put, this means they're competitors in the marketplace of superhero comics - though it's usually been a friendly rivalry. Still, this keeps the most famous and popular DC and Marvel superheroes from crossing paths outside of a few extremely rare official comic stories.