Confused

Ok I am 15+2 and 35 years old... I have a dr. Appointment tomorrow. I called them just to see what all was planned for the appointment... they said I would be having blood work. I asked if it was the NIPT cause all of the moms in the groups I am in are talking about the NIPT tests. She said no you are too far along for that you are having the AFP test. This does not provide the gender. I am disappointed because I wanted the NIPT so I could know. What is the main difference of the two? Thanks!