DC Rebirth has me a bit confused about the continuity, because I reading from some sites that Prime Earth shares the same history with New Earth (but are still separate), but with large chunks of history and memories being erased by an unseen force to change certain characters behavior and relationships, and another says Prime Earth and New Earth are the same continuity (and the page covering Prime Earth has New Earth as an alternate name and even the official DC site listed New Earth in the multiverse guide for Convergence and Mulitversity). Can anyone explain what's going on between the two I'm really confused?
Prime Earth - or for convenience's sake, the Post-Flashpoint universe - is a timeline shift, not a different universe.
So, it's a bit complicated.
Functionally, what Flashpoint did was reboot the timeline from the beginning - which means that the New Earth versions of the characters would be erased by the timeline shift. So, some of pre-flashpoint history still applied for the post-flashpoint versions of the characters, but they were different versions of the characters, in different times in their careers. That fact required that we split their pages between New Earth and Prime Earth (both of which are basically fan-names for Earth-0).
So, until Convergence, there was no way for Wally West to exist unless he was written into the universe as a new character (which he was).
What happened in Convergence, though, was that Brainiac - who importantly lives outside of the DC Multiverse and can travel through time - went to different eras and universes and stole individual cities from universes/realities that were about to be destroyed or erased. (And New Earth was one of them).
This meant that pre-flashpoint characters who were in the stolen cities could co-exist with post-flashpoint continuity characters (as well as several pre-crisis multiversal characters and elseworlds. etc.)
At the end of Convergence, Brainiac basically allows the heroes to undo/prevent whatever crises would have caused them to be erased/destroyed, and they all live happily ever after in coexisting, super-messy continuity.
What appears to be happening in Rebirth (mind you, I've only read the DC Rebirth #1 so far), is that defeating Darkseid (who, according to Multiversity is a character who exists in all universes), broke something that let Wally West from New Earth escape from the Speed Force onto Prime Earth, and "remind" people of the past reality the was erased. And I have to stress that again: New Earth was erased. Prime Earth and New Earth are not the same thing.
So, Wally making Barry remember New Earth is a wonky thing, because it doesn't make sense, but this is comic books, so it can happen anyway. There's precedent for it in books that were written relatively soon after Crisis on Infinite Earths, but overall, the idea is that only special characters who have been lost in some kind of comic book limbo ever really remember the way things were.
This does help, I was already confused by Convergence restoring the original and 52 multiverse (although wouldn't undoing the first crisis erase New Earth to begin with since it was created as a result of the first crisis?) and now with Rebirth trying to return several characters to there Post Crisis status, it was difficult to keep track of what is going on. But thank you for your help.
In Convergence The original Superman and Lois had their son Jon. They were trapped in Talos and Brainiac sent them back in time to fight crisis and defeat Anti-Monitor, and then Superman and Lois and their son went hiding in Prime Earth and disguise their last names as White. That's in the issue Lois and Clark and towards the end of New 52 when the Original Supermans new 52 Counterpart died from Kryptonite explosion in his head. In the beginning of the New 52 Justice superman the original superman watched his new 52 Counterpart the Justice league members fight Darkseid from distance away while the Original superman was standing on top of a building. After the new 52's death, the Original, Superman fought became the Rebirth Superman in the beginning of rebirth, and then the original Wally West came back during Rebirth, so the Original green arrow with the beard, and then the Original Superman and Lois merged with their new 52 counterparts, and them and their counterparts merged into one. Mr. Oz claimed that has merged the New Earth and Prime reality into One.