hey...
okie.. this is what i found out..
Forum : Would be a place for people to virtually meet online where they can post messages and respond to each other. These usually are set up to discuss a specific topic (ie. pets, computing, games,spritiuality and so on n so forth).
Newsgroup : Same as forum, an on-line discussion group. However to view and post messages to a newsgroup, you need a news reader, a program that runs on your computer and connects you to a news server on the Internet.
Note that with a forum you wont need a news reader.
Community : A virtual community is a group of people sharing common interests, ideas, and feelings over the Internet or other collaborative networks. Whenever you talk about a community its actually an "interaction" you are talking about. Blogs, forums, newsgroups etc are simply tools used to maintain this interaction
Hope this helped!!