It was many and many a year ago, In a kingdom by the sea, That a maiden there lived whom you may know By the name of Annabel Lee; And this maiden she lived with no other thought Than to love and be loved by me.
This poem begins exactly like a fairy tale, telling us that the story we are about to hear happened "many a year ago" in a "kingdom by the sea."
These little details are important, because the sea and this old kingdom will be big images in the poem.
Even more important though, is Annabel Lee. She's the title character, and she's the reason the poem exists.
The speaker introduces her in the third line by calling her a "maiden," which lets us know that she is young (and probably attractive), but which also keeps up the fairy-tale feel of the first few lines.
(You might think of her as being a little like a Disney princess, although as you'll see, this poem is way too dark to be a Disney movie.)
Finally, the speaker tells us the key fact of this poem, which is that he and Annabel Lee were in love. So much in love that it was the only thing that mattered to either of them.