Who/ What is Lenore in Poe's "The Raven"?

I could never really figure out if it was his wife or girlfriend but whoever she was Poe was lamenting her loss or in other words was dead and he was still grieving over her. When he first heard the tapping he thought it was her (her or her ghost, I don't know) but it says she was the fair maiden so wife, girlfriend, who knows.