BBY/ABY is used to position items along the Star Wars Timeline. BBY refers to Before the Battle of Yavin. ABY refers to After the Battle of Yavin. The Battle of Yavin in Episode IV: A New Hope occured in 0 BBY/ABY.
It is a period of unrest in the galaxy. The SithLord Darth Vader, enforcer of the GalacticEmpire, has learned that it was Luke Skywalkerwho was the rebel pilot responsible for blowingup the Death Star. Vader is now moredetermined than ever to track down his son andturn him to the dark side.
Luke, unaware that Vader is his father, fightsagainst the Empire with the Rebel Alliance. Newto the ways of the Force, Luke has discoveredthe journal of Ben Kenobi and has beguninvestigating any information he can on theForce-using Jedi Knights and their ways.
Through the underworld sources of his secretally, Dr. Aphra, Vader has received word ofLuke's location-the former Jedi temple on theplanet VROGAS VAS...