Faster transfer connection than USB,if your PC supports it,unit comes with the SATA to eSATA PC adapter.
I don't use as i only use laptop but i assume it plugs onto the motherboard SATA & you can join up to the Ext HDD with the eSATA cable.
eSATA is miles faster than USB. Not sure about the exact rate of transfer but either way. It connects the same way as USB- a connector on the back of supporting motherboards, or to an eSATA connector on a front panel, or via a chip directly on the motherboard.