In essence you have a portable, rechargeable computer hard drive. You download music, which you can do in subdirectories just like on a computer. You can also choose a search function, volume level, shuffle and random features through the hard drive's software and mechanical interface. You download songs to the device via USB or Firewire depending on your computer. It actually shows up as another drive on your computer. The rechargeable batteries in the Archos last 6 hours or so, at least on mine, before they must be recharged via AC Adaptor. DC Adaptor's are available but I did not want to add a lighter plug to my S, and 6 hours is plenty of music before I need a recharge break.
The Aux Port is in the glove compartment. The unit sits in the neoprene case in which it came. A male to male mini cable runs from the Line Out to the Aux Port. The Aux Volume Level is adjusted through the HK head unit.