What is the advantage of a balanced interconnect?

How does a balanced interconnect work (perform) as opposed to a regular interconnect?

I've been out of the "market" for a while and am a little behind. It seems "balanced" is better; however, one guy told me that unless I am running long lengths I don't need to worry about balanced interconnects. Equipment would be NAD or Parasound CD Player, undetermined DA Converter (the $3,000 question), tube monoblocks, and Magneplaner speakers (probably just 1.6's). [I think I hope to purchase a DAC with a volume control and run the interconnect directly to the amplifier - no pre-amp. I think.]

A quick primer on balanced interconnects would be appreciated. Thanks