I was a child and she was a child, In this kingdom by the sea: But we loved with a love that was more than love-- I and my Annabel Lee; With a love that the winged seraphs of heaven Coveted her and me.
In this stanza the speaker lets us know that both he and Annabel Lee were young when this happened. Not teenagers even, but kids: "I was a child and she was a child."
This lets us know just how rare and special their love was, but it also tips us off that maybe there's something not quite right here.
He also repeats the line: "in the kingdom by the sea." This reminds us where we are, but also creates the hypnotic, repeating effect that Poe loves.
It's the same trick he uses in the next line, when he tells us that he and Annabel "loved with a love that was more than love." He wants to let us know that their love was special and intense, even though they were so young.
So, the speaker uses the word love three times in the same line, which is a pretty gutsy move for a poet.
This love was apparently so amazingly strong that the "seraphs" (that's just a fancy word for "angels") in heaven noticed them.
In fact, these angels apparently "coveted" the two young lovers. That's a kind of tricky word, but an important one for this poem. To covet means to want something really badly, usually something that doesn't belong to you. This is a strange feeling for angels to have, since it's definitely not a holy emotion. It's also our first hint that things might not turn out so well for these two kids.