Can a dev. please clarify about party system?

Can a dev. please explain what actually happens when u form a party. I have been seeing a lot more people telling me to join their party so we can all share the xp. I know this is common in most mmo's, but thought it didn't apply in AL. I assumed as long as ur close enough to the kill u would get the xp also. Can I get some explanation to how the whole party system works.

Parties allow you or other members of the party to join another person in the party. It ensures that no one joins you or any other member in any campaign map. And yes, if you're close enough, you should be getting some xp unless you're capped or have your xp gain disabled.