How does Huck Finn end?

Could you please elaborate on the conclusion of the novel "The Adventures of Huckleberry Finn" by Mark Twain? Specifically, how does the story of Huck and Jim's journey down the Mississippi River come to a close? Are there any significant events or resolutions that occur in the final chapters that provide closure to the narrative and its themes? Additionally, what impact does the ending have on the overall message and meaning of the book?