The poem has two speakers: one opens the poem with a series of questions, and the other closes the poem with the answers to those questions.
The first speaker sounds like a reporter doing an interview. He (and we know it's a he because the second speaker calls him "Sir" in line 10) is concerned with the legacy of the people of Vietnam, who, in the poem, have been entirely wiped out by a bomb. This speaker is curious, too, about the culture of the people, asking about their ceremonies, poetry, songs, and even the ornaments they had in their homes. All of these questions reveal an interest in the lasting influence of Vietnam and a curiosity about whether anything has been preserved to create that influence.
The second speaker has more knowledge of what happened to the people, though he (or she—it's not clear) doesn't provide any concrete answers. All of the culture is lost, he or she says, because all of the people have been lost. They have no way to know how the people of Vietnam lived because nothing has been preserved. This second speaker is a bit more clued-in—declaring, for example, that "All the bones were charred" (18)—but we don't get the feeling that this is necessarily a good thing. Instead, our second speaker is intent on emphasizing the great loss.