The end of lord of the rings?

They are leaving middle earth back to go back to Arda which is sort of like a pseudo heaven where immortal creatures such as elves and vala (god type things) live. Usually mortals are not allowed there, but Frodo and Bilbo earned their way by carrying and being irreperably damaged by it. Arda is the only thing that will bring them peace. All the elves get to go if they want because they are immortal and originally came from Arda to middle earth. None of this is really explained in detail in the movies. Elrond just makes a few mentions about it. All this stuff comes from Tolkein's book The Silmarillion.