A message board is an online discussion area in which users with similar interests discuss topics. These conversations or discussions are available in the form of posted messages.
Discussions are listed in a central place maintained on web pages. Message boards can be specialized or general, global or local, free or subscription-based, public or private, etc.
Due to the simplicity and uncomplicated accessibility, message boards have become an excellent source of discussion and communication on the Internet.
In these friendly discussion spots, members are able to view posts, post new queries or respond to existing queries posted by other members.
A message board is also known as a forum, an online forum, and Internet forum or a discussion board.
Source : www.techopedia.com