both are either short or long positions.  I always play the short position.  Both incorporate 4 legs selling both a Bear Call spread and a Bull Put spread against a position....at least in regards to the Iron Condor.  A butterfly is a similar tactic using either Puts or Calls with a central short strike price at/near the underlying's price.

Iron Condor explanation:

http://www.theoptionsguide.com/iron-condor.aspx

Butterfly explanation:

http://www.theoptionsguide.com/butterfly-spread.aspx

There is also Broken winged butterfly spreads and Christmas tree spreads, as well as ratio spreads.  Rarely, will I employ one of these strategies, but they are good to know about.