The alternate reality was a new reality created when a temporal incursion caused by time travel of the Narada, a Romulan mining vessel from the year 2387, disrupted the time continuum. Accidentally traveling back to the year 2233, Nero, the Narada's captain, attacked the USS Kelvin. The attack resulted in the deaths of several crew members of the Kelvin, including George Kirk and Richard Robau, and the destruction of the Kelvin itself. Spock arrived to the alternate reality in 2258 and was captured by Nero, who used red matter to destroy Vulcan. However, Nero's attacks united the crew of the USS Enterprise, who foiled his attempt to destroy Earth. (Star Trek)
Om du är bekant med Mirror Universe från TOS och DS9 - det är samma typ av koncept (även om , ett annat alternativt universum)