In the story, To Kill a Mockingbird, what purpose does Dill serve in the novel?

In the book "To Kill a Mockingbird" Dill serves several purposes.  The first purpose is as an outsider looking at the events occurring in the small town of Maycomb.  Dill is worldlier than the children.  He has been raised in different cities and seen different things.  He has even had the opportunity to attend movies.  Dill's character allows the reader to view the situation of Tom Robinson's trial and treatment from a perspective other than Scout's and Jem's.

Dill also serves as an example of a different type of home setting.  His life has been one of tug of war between families, an unsafe and unhappy environment, and very little control in his ability to make decisions.  Scout and Jem have come from a good home with consistency.  Atticus lets the children learn through discussion and example.

Dill is also a catalyst for the events that follow with Boo Radley.  He wants to play a scary game with the children after he learns about Boo.  Jem runs and touches the house.  The event sets in place other events that follow that eventually lead to Boo saving Jem and Scout from Bob Ewell.