Joseph Brodsky said that a poem consists of exposition, argument, denouement. I suppose by "argument" he means engagement or struggle with the elements that have been uncovered during exposition. And I sort of view that part of the process as the "turn," or where a shift in perspective begins or a a deepening occurs. And I like what Mike Finley has said about the denouement -- it's where something new appears in the poet's consciousness, some insight the poet has achieved after exposition and engagement.
I like what Brodsky and Finley think about this stuff. It emphasizes the idea of craft in poetry. Like in music, where sonata form is a structure on which to hang invention. Of course, there must be freedom and spontaneity. But craft is a way of saying: "Poetry is a form of art and should be shaped according to implicit standards."
I'm still learning the ropes.