The Werewolf and Vampire Treaty and their Truce
Werewolves and vampires have always been enemies, but they have laws just like us. The most important law for werewolves and vampires is the treaty. That means that they both have territories where the other cannot go. This helps keep the peace. The treaty between werewolves and vampires is alot like animals, if (for example) a male tiger has territory he will not let other male tigers live there with him.
But the Volturi lead by Victoria, who wants to get revenge on Bella for killing someone she loves, is creating an army of newborn vampires to kill Bella. When the Cullens find out, they need all the help they can get to stop the army of newborn vampires and so they have to ask the werewolves. The vampires and werewolves form a truce and start to train together and trust each other.
The truce is probably one of the most important events in the book, it is significant to the story because it gives the author a way to make it make more sense even in this fantasy world, because by the things that Stephanie Meyer has written I doubt that the Cullens could defeat an army of newborn vampires so this gives the author a way so that it is not too easy to kill the vampires. she makes so that it is not like in the Lord of the Rings movies where it is WAY to easy to kill an army of thousands of orcs.
The truce is important to the characters because it means that the ancient enemies have to find a way to work together and it's a way to get both people who love Bella having to be in close proximity.