The original Earth-Two was the original DC Earth, with superheroes starting in 1938 with Superman, Batman in 1939, and so on. On Earth-Two Clark Kent worked for the Daily Star, not the Daily Planet, his Krypton was a race of superhumans, and Wonder Woman came to man's world not as an ambassador but to help America fight the Nazis, just to cite a few differences. The Flash and Green Lantern of Earth-Two were Jay Garrick and Alan Scott, and the main superhero team was the Justice Society of America, who were formed in 1940. DC Comics from 1935-1951 were for the most part sat on Earth-Two, although that fact was retconned in later. Earth-One is the more familiar world with the Barry Allen Flash and Hal Jordan Green Lantern, etc. DC decided comics fans were too stupid to comprehend a basic science fiction concept like alternate Earths and so ignorantly did away with their multiverse system in the 1985 series Crisis On Infinite Earths, resulting in a single clutterearth and negating all the stories ever written for their 3 most famous characters by the characters creators. They also destroyed all their continuity, ruined Superman, and butchered Hawkman and the Legion of Super-Heroes so badly that they have never recovered and have become irrelevant.
Over the years, DC has teased returns to this multiverse system, and finally brought it back in the horrid Infinite Crisis series. Since then, DC has had another reboot (the third such reboot since COIE "fixed" their universe), and there is a new Earth-Two that is different from the original one but is trying to squeeze a few bucks from JSA fans by using the names Alan Scott and Jay Garrick. This new Earth-Two will be the typical grimdark superhero world because comics are now read by emo loser nerdy adult men who get their sick jollies off on death and gore instead of kids, who have abandoned comics and get their fantasy adventure from stuff that is actually worth a **** like Harry Potter.
