What is a Wiki?

In a recent post, Simon Meth predicted as his 2006 Prediction #8, that "Recruitment wikis will get started. HR leadership won’t know what a wiki is."

This post presents me, an HR leader, with a professional challenge since I don't know what a wiki is. Yes, I am aware that there are things called wikis out there, but I don't know exactly what they are. How they could be of value or benefit to me  or how they can effectively be used as a learning tool? I did contact Simon and he referred me to the Human Capital Institute's free webcast "Collaborative Learning Technologies: Wiki's and Blogs and More, Oh My!"  As you would have it, the webcast is this Friday. I have cleared my calendar and, barring any catastrophes, I am going to learn about wikis.

Recruiters are starting to use wikis, the physical education teachers at G-Town are getting wiki . . I want wiki too!