Forum - An online 'bulletin board' upon which users can post topics for discussion.
Blog - Short for 'weblog', an internet journal that is updated regularly.
Post - A new article in a blog or a new message in a forum. To 'post' something is to publish something on the Internet.
Tag - A word or phrase that sums up the contents of a specific post.
Thread - A discussion that takes place in response to an initial post.
Wiki - A community that seeks knowledge, in which the users contribute and edit the knowledge.
Group - A group of users who share a common interest or theme.