A wiki is a web site similar to a blog in that you share information. Wikis allow participants to continuously edit the page, rather than just comment on it. Wikis provide a place for online collaboration and sharing. Wikis have different privacy settings which can protect the page from outsiders viewing the information. Participants need to be invited and what they can edit and change can be set by the leader/creator of the wiki. For more information on what a wiki is and how to use one, you can visit the Wiki Walk Through.
Wikis are a wonderful way for teachers, parents and students to collaborate and be able to share information with each other. Many teachers I know have accounts with http://www.wikispaces.com/ and they use their wikis for many purposes. One teacher at my school used it for students to discuss chapters of a book that they were reading in class. Another uses it for homework discussion. I have thought about several ways that I might use one with my second grade class and have a few ideas that I think will work well for primary grades.
Several years ago our school did a training on using wikispaces and everyone signed up for an account. I felt that the session was information but at that time I didn't utilize the wiki on my own. I had forgotten the step of applying for an account through the county to make sure it was a secure site for students until I read a blog of a classmate, thanks for the reminder Katie! I have applied for my wikispaces account through HCPSS and hope to hear back soon.