I've been interested in BPD for a while, but I have never understood the lacking an identity symptom. How can you not know who you are? I am asking out of genuine curiosity, because it doesn't make sense to me.

Is it like not knowing what job to pick, or what direction to go in life? Or does the criteria refer to not knowing what personality traits you have? Is it about not knowing how you appear to others, or about not being in touch with your physical nature? All of the above?