Below is the definition of Discussion Boards, for a definition of blogs and wikis see their corresponding pages.

What is a discussion board?

A Discussion Board is a communication tool that allows individuals to collaborate with others through posting or answering questions. Also referred to as forums, message boards or bulletin boards.

The differences are:

Blogs:
1. Are personal
2. A posting is owned by a poster (could be owned by a small groups)
3. Aim is conversation, change in thinking/self/ideas, writing of the moment
4. Content is considered to be static: once posted, the posting doesn't change (comments can add information to your posting)
5. Content is displayed in reverse chronological order and scrolling is required
6. Comments are optional but encouraged to continue the conversation
7. The intent is personal, news, reflection
8. Voice used is conversational


Wikis:
1. Open to collaboration
2. Topics are considered public space and owned by all
3. Aim is creation of documents
4. Content is not permanent, it can be revised by any one
5. Content is displayed in nodes/tree structure
6. Comments are not expected
7. The intent is informational
8. Voice used is passive and active


Discussion boards:
1. Open to collaboration
2. Are owned by groups with equal responsibilities
3. Aim is to provide support
4. Content is considered to be static: once posted the posting doesn't change (answers are provided by others)
5. Content is organized and presented in different ways
6. Answers are required
7. The intent is decision making (used more to provide support)
8. Voice used is conversational