wikis - thing 16

Wikis? I had heard the word, knew it meant something with the internet, but what? Now I know, thanks to the 23 things. I had seen the wikipedia come out from an internet search, but thought it was an encyclopedia, like World Book. But this encyclopedia, wiki, can actually be changed, as far as adding, deleting, etc. That is odd. I agree with one blog I read in one of the library wikis, that they did not put much value in the wikipedia, that they always checked with other permanent sources, to get concrete info. Wikis would be hard for me to use alot, I need organization, and surity.