In this video CBS political analyst Jeff Greenfield explains how the Iowa caucuses work for both parties. The caucuses for both parties function very differently. The Republicans' Iowa caucus process is the much simpler one. It is very similar to a straw ballot with voters casting secret votes on a piece of paper. The voting process used by the Democrats is public. It is quiet complex and involves people standing in designated areas to support their candidate of choice. The Democratic candidates also need to achieve at least 15% support or their supporters can leave and go home or switch their support to another candidate.
Jeff Greenfield - who was a political analyst on CNN for many years before joining CBS - always manages to make complex political issues much easier to understand. If you want a written explanation of how the caucuses work you can read about the process here on Wikipedia and here on the Iowa Caucus website.
