One Piece Film Strong World: Episode 0 is the animated version of Chapter 0. The OVA was released in Japan at the end of April 2010, in a limited edition run of 3000 copies. House Foods ran a contest during November 16, 2009 and January 15, 2010 and the winners received the Episode 0.
Based on Chapter 0: Chapter 0 is called “Strong World“. It is a special chapter released with Chapter 565. It introduces the events 20–25 years before Monkey D. Luffy began his adventure, and the story of Shiki for the 10th One Piece Film: Strong World.
The episode contains the details of the Edd War and its aftermaths from 20-25 years before Luffy set out on his journey. After the Edd war Roger (Pirate King) was arrested*(actually he turned himself in). After hearing the news about Roger, Golden Lion Shiki attacked the great prison Impel Down but was defeated by Garp and Sengoku. He was kept in Prison for two years but after hearing Roger’s execution he broke out of Impel Down loosing both of his legs in the process. Before his execution Roger started The Great Pirate Era which we now know of.
For more details I suggest you to read the Chapter 0 or watch the episode.