Sorry, but I have to disagree with this website's definition. I was pretty sure that I was right and I double checked in my dictionary and also in Gray's Anatomy before starting this reply.
Vulva refers to the external genitalia as a whole. This ends at the introitus, or opening into the vagina, which is part of the internal genitalia. In other words, vulva include the labia, the clitorus, and the vestibule (which is the space between the labia).
I guess this may be a minor point. After all, a genital by any other name will feel as good.