Colposcopy appt after receiving normal smear test results letter??

Hi, This is my first post so apologies if I'm doing it completely wrong ha ha! I went for my first ever smear on 15 Sept and received my letter with results saying it was normal and I have a very low chance of cervical cancer but got home today (14 Oct) to a letter with an appt for colposcopy has this happened to anybody else before? And is it usually because you're high risk HPV? Not that I know entirely what that means! I've been googling but can't find any definitive answers. Thanks