What's the Original Idea Behind Wikis?

The original idea behind wikis was like the way Linux systems used to be mostly unpassworded, right? Like your email account wouldn't have a password because why would you need a password? I do think some of that is coming back somewhat ironically through what isn't an open source wiki. There are some that only have like three or four people contributing to it, which is interesting and cool. It's something you can program to just pound every server in the world.