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.
Lowbacca has left the Jedi academy and traveled to the planet Ryloth, headquarters of the Diversity Alliance, to see what the Diversity Alliance is really all about. On Yavin 4, Jacen, Jaina and the other young Jedi Knights have already discovered one truth about the Alliance—once you go to Ryloth, you either join or you die. Lowie is in great danger, and they must rescue him. But what can a small group of humans do against a planet full of hostile aliens?