There are many "why" and "how" questions we could ask about "The Tale-tell Heart." For example, we could ask, why does Poe choose to use the first person point of view of the murderer to narrate the story?
We could answer this by saying that Poe uses the first person point of view of the murderer because it makes the story much darker and creepier and interesting. The narrator is unreliable; he questions his own sanity ("How, then, am I mad?") The reader is constantly questioning the validity of what the narrator is saying.
Moreover, by using the first person, the reader is in the mind of the murderer. We see, hear, and feel what he does. At the end of the story, we are in the narrator's mind as he is driven mad by the beating of the old man's heart, as he perceives it, which leads him to confess his murder to the police:
"'Villains!' I shrieked, 'dissemble no more! I admit the deed! --tear up the planks! here, here! --It is the beating of his hideous heart!'"
We could also ask, how does Poe's use of repetition throughout the story add to the ominous tone? We could ask, why is the story called "The Tell-tale Heart"? These are just some examples of questions that can be asked.