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.
The planet of Naboo has been blockaded. Obi-Wan Kenobi and Qui-Gon Jinn have been sent as Jedi emissaries to establish peace. But they find war instead.