I just came across the word 'Burden Resistor'. Is it any different from a normal resistor? 

If it is different, where can I possibly get one?  [Sparkfun][1] hasn't got one listed.  Any help is appreciated. I am trying to build a [current sensing circuit][2].


  [1]: http://www.sparkfun.com/search/results?term=burden%20resistor&what=products
  [2]: http://openenergymonitor.org/emon/node/58/