Earth Prime is a term sometimes used in works of speculative fiction, most notably in DC Comics, involving parallel universes or a multiverse, and refers either to the universe containing "our" Earth, or to a parallel world with a bare minimum of divergence points from Earth as we know it — often the absence or near-absence of metahumans, or with their existence confined to fictional narratives like comics. The "Earth Prime" of a given fictional setting may or may not have an intrinsic value to or vital connection to the other Earths it exists alongside.
Earth Prime
In most of the DC Comics media, the Multiverse is a "cosmic construct" composed of the many fictional universes the stories of DC media take place in. The worlds in the multiverse share a space and fate in common, and its structure has changed several times in the history of DC Comics.
A depiction of several alternate Earths within the original DC Multiverse before the events of Crisis on Infinite Earths and the variations of the Flash inhabiting each Earth, art by Dan Jurgens and Art Thibert.