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 Youtini Expanded Universe Ranking system is a 1-5 scale that ranks EU book quality, difficulty, and importance. Books closer to Level 1 are easier to read and understand, more important, and of higher quality.
When Anakin's classmate and aspiring Jedi Uldir fears he is not learning fast enough, the discouraged youngster steals the Holocron, a powerful and ancient Jedi treasure, and Obi-Wan's lightsaber.