Wikis in plain English (ADVANCED)

Hi there! Look at this! Have you ever heard of wikis? I know the wikipedia, but actually, I have to confess the first time I heard of wikis was two or three weeks ago when my students of the 4th year explained it to me. In case not everybody knows about it, watch this video where you have a perfect explanation in plain English. If I knew how to do it, for sure I would include wikis in my blog... so, please... can you help me? I think we would all find it very useful for written debates!