A2000 What Card Is This?

[Ofoosy]

I got my first Amiga quite a while back from this old man on  craigslist  and I haven't really done anything with it because of some  problems I  have with this card that have no idea what it is it has a  port where a  hard drive goes (and it came with one) If the card is  plugged into the  Amiga it wont boot if its removed it works just fine  and its just that  card and nothing else
 
Does anyone know what this card is and what it does