An internet forum, or message board, is an online discussion site.  Forum members or guests create content that is organized into discussion threads.  Typically there is a moderator that helps keep things organized and facilitates an active message board.

People that participate in the forum often will form bonds around a particular subject.  Popular forum topics include parenting forums, expectant mother forums, neighborhood forums or sports forums.

Here is an example of a forum.

It is always important to remember that posts on a forum are often read by a larger audience than posters (people who post messages on the forum regularly.) 

Readers that follow a forum but do not post are called lurkers.  

A poster that consistently breaks the rules of forum etiquette (often called netiquette) or posts inflammatory or derogatory messages is called a troll.  Generally it is the responsibility of the forum members to report a troll to the forum moderator.  The moderator can choose to ban the troll from the forum.

As forum members get to know each other, sometimes things can get quite personal.  Some posters may make up personas.  If your relationship with the forum posters is purely an online relationship it is important to always use caution when posting personal details of your life or including photos.

Forums are often fun ways to connect with people that have similar interests as you.  They are great ways to generate new ideas and facilitate unique discussions.  It is a great way to create or strengthen a community.