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.
All your favorite Star Wars characters – Luke Skywalker, Princess Leia, Han Solo, Chewie, the droids, and others – are bringing peace to the recently liberated galaxy after Return of the Jedi. Even without the oppressive Empire, the young Republic is finding that there are still troubles to confront, and battles to be won!