The 'miniDV socket' is probably just a 4 pin firewire port. This will be clarified in your manual. Here is a picture of a 4 pin firewire port and here's a picture if a 6 pin port.
Anything that is called FireWire, i.Link, IEEE 1394 is all the same thing and is the interface typically used by DV video cameras to transfer video to the PC.
Most likely you just connect this to your PC and use any DV capture application to transfer the video into .avi files.
As to the USB port, the camera probably takes photos as well and you transfer the photos by USB.