Wiki What?

I'm quite completely lost with Wickis. I had a look at the suggested wickis with my favourite being Wookipedia - it would have been helpful when one of our staff was asked to answer how tall one of the Star Wars characters was and then how tall that would be with heels on!
I get Wikepedia where you can add to the information but I get lost a bit with some of the fancier wickis. They must be staff only wickis and if that's the case why would you use this medium for that information such as the Mint Museum wicki. Weren't there any Australian based wickis? The Library Success wicki was all American and hard to relate to. I could look for wickis with Australian content but I can't tell with some of the listed examples whether I'm looking at a wicki or what?

If I can work this out a bit more I think a wicki would be a great way of a group working over distance to keep in touch. At the moment I am involved with a group that includes people from outside the library and this would be a great way of everyone keeping up to date. I'm not sure I really like the thought of everyone in the group being able to change my ideas though. If it's changed I might forget what the original thought was especially if its changed by someone who has missed the point of what I was trying to say.