What's a caucus?

Iowa caucuses 101: Arcane rules have huge impact on outcome:

"Supporters of candidates making up less than 15 percent of the vote in a particular precinct will have the option of making their vote count by voting in the second tally for a 'viable' candidate -- one that got at least 15 percent of the vote on the first tally.

It is particularly interesting to watch what happens between the first and second tallies at the Iowa Democratic caucuses, as viable candidate camps vie for the votes of the unviable. It's one of the few times in American politics where voters directly interact with each other.

During the 'persuasion' time in between tallies, the precinct captain for the viable candidates sends a person over to each group that failed to meet the threshold to convince them to support their candidate. Once everyone has decided where to vote, a second tally is taken, and the results are then sent to Democratic state party headquarters -- not electronically but via ordinary mail."

I am so not a politics person. I look up the meaning of "caucus" every 4 years because I completley forget what the heck it is by the time the next one rolls around. I read stuff like that and my brain just shuts down and I start looking for something shiny to stare at.