Storyline
From GuildWiki
Each Campaign of Guild Wars has its own PvE storyline. The stories of the first two chapters take place almost concurrently. Nightfall takes place 3 years after the events in Tyria and Cantha.
Players traveling from Tyria or Elona to Cantha will jump into the story about 20% of the way, and players traveling from Cantha or Elona to Tyria will jump in about 30% of the way into that story, and players traveling from Tyria or Cantha to Elona will jump in about 10% of the way into the story.
Here are the storylines of each campaign: