A forum, or community section, is an easy way to add useful content to your web site with very little effort. First of all, let's define what a forum is. A forum is a place for users to hold discussions on various topics. It is interactive, in other words users can both read postings and post items themselves. Let me give you a half fictional example of a forum in action.
Forum Thread, Subject UFC in Canada on a Mixed Martial Arts site.
[USER1] Has anyone heard that the UFC might be holding an event in Canada?
[USER2] Yes, I heard that. In fact, I heard that George St Pierre will be on the card and it will be at the Bell Center.
[USER1] Thank you USER2, I can't wait to get my tickets.
[USER3] Actually, I heard that it's been canceled and George St Pierre is out with a knee injury.
So, you can see that the web master has gotten some valuable content with no work on his/her part. The users are able to ask questions and respond to them. Once the forum is set up initially and you've found a way to get traffic to your forum, it becomes a perpetual content machine, generating useful content for your web site and hopefully in the process some revenue based on some sort of ad or affiliate program, like Google AdSense or ClickBank.
Lets try out one more example Thread, this time from a software forum
[USER1] I'm trying to find a link to the phpBB web site and can't find it anywhere, does anyone here know what the URL is?
[USER2] You could try doing a Google search on phpBB. It should be near the top of the search results.
[USER1] Thanks, USER2, how about a guide on how to install phpBB?
[USER2] Do a search on "Installing PhpBB On GoDaddy", or there is also a guide included in the package.
[USER1] Thanks again for the help! Once I get my forum up and running, I'll post the URL here for you to take a look at.
You can see how the interaction works. It's not always question and answer, a lot of the time, somebody will post some new information they discovered, or expereinces they've had (like on a travel forum).
There are two driving factors which make forums popular. The first is what drives the posters/question answerers, this is either fame or promotion. They either like seeing their name in lights, or they have a link to their web site in their signature (I allow this on my forums as long as they are posting useful information).
The driving force for the people reading the forums is the need for information. Computer forums are extremely popular in this area. People need help finding drivers, installing software, diagnosing problems. People want reviews of products one on one, by other users who don't have a vested interest in what they end up buying. Forums are an invaluable research tool for these people, and by the way, the ad links on these pages also turn into information sources for the same people.
Adding a forum to your web site is also not expensive or difficult. You have several options in the forum software arena, some of the most popular are vBulletin an excellent choice where licenses go for $150US and my personal favorite phpBB which is a free open source product.
When making the decision of paid vs free software, it's always important to figure out what kind of user you are (experienced vs novice), how much hand holding you require and of course if the paid version really any better than the open source alternative.
Support can also be an issue to be considered, with some smaller open source projects it can be difficult to find help and/or expertise. I haven't personally used vBulletin, but I have read several reviews and looked through their support offerings they offer 1 month, 6 months and 12 months of phone support for $60, $180 and $300 respectively. vBulletin also offers professional installation at $135 per license.
Most forum software, including phpBB and vBulletin, require you to have PHP and MySQL available on your host. This isn't an issue with most web hosts such as godaddy, or hostgator.
If you have a little experience in installations and setup, I would recommend at least giving phpBB a try. Set up a sub directory on your web site, install it and see how it goes. The installation instructions are excellent and if you find yourself installing on GoDaddy, do a search on "Installing PhpBB On GoDaddy", don't forget the quotes. If you're installing on hostgator, or most others the install instructions included with phpBB will do just fine. If you still find yourself having problems, the folks at the phpBB web site (on their forum) are quite helpful.
There are currently two version of phpBB, 2.0.x which is a stable, production ready release, and phpBB 3.0 which is still in the beta stage and is looking good. For now, I would recommend installing 2.x and look to 3.0 in the near future.