Forums are a great way to share information. Unfortunately it didn't take long to learn that you can't just let people post whatever they want or you will end up with a forum that nobody wants to visit. This is why almost all forums these days have moderators. If you are going to spend time at a forum you will need to be familiar with the moderator and what they do.
The job of a moderator is to make sure that what is being said in forum falls within the rules that have been set for that specific forum. The main task that they have in a lot of forums is to put a stop to arguments. The anonymous nature of forums tends to lead to people saying things that are not really appropriate and this often leads to arguments. In a lot of cases these can get quite personal. This is not the sort of things that the forum is going to want to have on its site so the moderator will put a stop to it if things get out of hand.
The other big task that forum moderators have is to keep internet marketers from taking over the forum. Most forums will tolerate a little bit of marketing as long as it is done in a subtle way. Unfortunately a lot of marketers will simply put up posts that are little more than advertisements. Clearly this is not something that the forum wants, not a lot of people are going to read the forum if all they see is ads. Therefore the moderator will get rid of posts that are overly promotional.
A lot of times people will make posts that are not really relevant to the content of the forum. This is more of a problem on forums that are on a tightly focused niche than it is on more general forums. In these cases the moderator will take steps to keep the discussion limited to the intended topic of the forum. This is done to ensure that the niche forum does not expand beyond its intended subject and become a general forum in which a wide variety of topics are discussed.
There are several different ways that a moderator can control what is said on a forum. The most common of these is a warning. This is most commonly used when a disagreement is starting to turn into a personal argument. In this case the moderator will warn the participants that they starting to go too far. If this does not work the moderator may remove specific posts or even whole threads. This is also what they usually do when things are getting off topic or overly promotional. If somebody is consistently breaking the forum rules the moderator may ban that person, either permanently or for a specified time period.