It's the clitoris and it does get erect especially when you pull back the hood and do a few things in my bag of trick and for the ones that want a sure fire way not my secret weapon but a simple lift clit hood then do gentle circles near clit base with tip of tongue and mix it up and be nimble and know this is not tough and the reward for good word is her eyes rolling back in her head and a juicy snack that'll have to be cleaned up while your down there no matter how long it takes and be thorough and check everywhere down there and double or triple check if you want to make the best impression. :D