Ok, on your mobo (motherboard), there are 2-6 (depending on your mobo) of these 2-2.5 inch white slots. Those are your PCI slots. stuff like tv, sound, modem cards go there. Then, at the end of the rows of PCI slots, there is a dark brown slot that is fixed a little further into the mobo, it's right next to the last PCI slot (not on the edge of the mobo; the interior). That is the AGP slot. In case you don't know what it means (which I'm sure you do): Accelerated Graphics Port. Just by the name, one can tell that the video card goes there.
This explanation is what I'm assuming your asking.
If you are asking if the video card itself is an AGP or PCI, then it should say on the box, or in the instructions. Seeing as it's a new card, then it's probably gonna be AGP, although there is the occasional card that is a PCI slot card (kinda stupid, 'cause there is a completely seperate slot for it, so y put it in a PCI slot?)