Well now this is unusual. Our speaker's being so upfront: "Hey this is a poem; welcome." We also get a sort of vague definition of poetry: something silly and comforting. Which kind of makes sense. We mean, from a certain perspective, spending so much time with a few words on a page is kind of silly. As for the "comforting" part, well, we guess our speaker believes that poetry can provide a sort of consolation or encouragement. But we'll have to keep reading to find out if that holds water.
It is not the sunrise (1.2)
So now that we've been introduced to the poem, our speaker begins defining what the poem is not. Right at the beginning, our speaker wants us to understand that a poem is not the same as the things it describes. Although this might make us scratch our heads, it actually kind of opens up the possibilities. Once we quit thinking of poems as simply being pieces of the world, we can recognize that maybe they're a lot weirder than that. They refer to things in the world, but they kind of exist on their own little plane.
it is not the mockingbird who, in his own cadence, will go on sizzling and clapping from the branches of the catalpa that are thick with blossoms (1.8-10)
In this description, the speaker shows poetry's knack for conveying amazing images. Even if the poem-world is not the same thing as the real world, it still refers to it and can impact us through those references. Our speaker might remind us, though, that the transformative awe we experience when reading that description is an entirely different experience from the transformative awe we might feel if we saw the scene in our backyard.
The poem is not the world. It isn't even the first page of the world. (8.1-2)
Here our speaker states outright what we gathered she was saying when she told us that the poem is not the sunrise, the beetle, or the mockingbird. By adding that the poem isn't "even the first page of the world," she makes it even clearer—the poem is its own thing. Sure it might exist in the world as marks on a page, or sounds coming from our mouths, but the words and meanings really only exist in our minds. It's like a shadow world, which we kind of base off the real world, but which has its own life. Head spinning?
It wants to open itself, like the door of a little temple, so that you might step inside and be cooled and refreshed, and less yourself than part of everything. (8.5-8)
Just because the poem isn't the world doesn't mean it doesn't have life in it. So how does a poem want something? We think it has to do with the way many poets feel that poetry takes on a life and a will of its own. They can't bend a poem to their will, or at least it won't be a very good poem if they try. Some poets express the experience of writing a poem as submission to it, as if there is a truth or quality that wants expressing and they are simply (if they're lucky) able to uncover it.
This is the dark bread of the poem. This is the dark and nourishing bread of the poem. (12.18-19)
So the last word of the last line is the same as the last word of the first line: poem. Coincidence? Probably not. Our speaker is definitely concerned with this poetry business. We guess she figures that if we're going to be reading poems, we ought to be concerned with what they are and what they can do. As for "dark bread," we think that means the core, the kernel, the important part. Bread, after all, is one of the most basic forms of food or sustenance. So the core, the nourishing part, of the poem might be what the speaker conveys in the line before: "Live with the beetle and the wind."