Lord Byron was a poet from the Romantic era and was somewhat of a playboy in his time. He spent a lot of time with women and dealing with love affairs. This poem, however, is about a woman whose beauty exists beyond, and perhaps above, the sexual attraction he is accustomed too. The unnamed woman he writes about contains the beauty of both the light and the dark. Her love is "pure" and she has a sort of beautiful sense of innocence to her. This is a kind of beauty Byron is not used to seeing or experiencing, so just by looking at her, and without knowing her all to well, he receives all these feelings and notions about her. He is struck by her innocence and purity so greatly that it takes him out of his world of sex and loose morality for a moment so he may marvel at her beauty, and that is why he writes a poem about her. This poem itself is a detailed description of this unnamed woman's beauty, a beauty so rare to Byron that he cannot help but be completely enamored with her for this brief moment, only to ultimately fade back into his world of meaningless sex and love affairs.