Question about vulvas?

Ok, this is a little bit of a strange question to be asking but I am very confused. Looking at a woman straight on should the top of her vulva just look like a slit? Mine protrudes slightly and doesn't look like a slit.. what is this? I am aware that everybody looks different down there I'm just wondering why some people just have a 'slit' and some people have the protruding part? (I'm talking about a frontal view of the vulva..)