Wiki

Today I did the Wikipedia assignment at home since I had both time and access to a computer. I have used Wikipedia before for recipes but didn't really understand the concept of a wiki. I could see a wiki being used by people at the library to give stable (as opposed to changeable) information about our library or information about community services, ongoing community programs especially ones that the library is involved in (Summer Read for example), etc.
I did appreciate the comment that one of my fellow library bloggers made about getting information with accuracy issues.
Two questions: I thought I was on the correct week lesson but I see Week 8, am I behind and did I miss Week 7 someplace?