Basically, he's a Superboy who comes from the "real world" (which is meant to be ours) but his world was destroyed during Crisis of Infinite Earth in 1985, and he was exiled into a pocket universe with Earth-2 Superman, Lois Lane and Earth-3 Alexander Luthor.
Fast forward a few years after the Dark Age of Comics, they saw what happened to the DCU without them, and the whole group was disappointed, so that Superboy punched reality so hard, he actually freed everyone in the pocket universe and retconned some stuff in the DCU. They decided to recreate the multiverse in the Infinite Crisis event, during which he was written as going insane and jealous of the current Superboy, killing and maiming a good chunk of people.
After that, he was involved in a bunch of adventures (almost all of them from Geoff Johns) where he was treated as a dangerous psychopath and the voice of people that thought "It was better before" in DC.
Note that he's aware of the fourth wall and often comment on it.

Seems like a wasted effort to try and redeem the screeching man-child that brutally beat to death OG Superman.

Then again, I've no idea how he's handled in New 52 or Rebirth, if he has much presence at all.