There are a lot of people who use forums every day. On the other hand there are also quite a few people who have never used one. Part of the reason is that there is a belief in a lot of quarters that forums are mainly for IT related subjects; this is certainly not the case.
It is certainly not the case that forums are only for IT subjects, these days there are forums for almost any possible topic that you can imagine. In fact there have been forums on a wide variety of topics since the very first days of the web. The very first forums were started in the seventies long before the web even existed. These were bulletin boards where people could post messages. Back then the only people who used these bulletin boards were computer enthusiasts so this is largely what they talked about.
Even back in the seventies however there were forums that covered other topics. The people using the bulletin boards realized that they had a lot more in common than just an interest in computers. In the early days they just posted whatever they wanted on the bulletin boards as they really weren't organized by subject. It didn't long however for the realization to set in that this made it hard to keep things organized. Therefore there were boards created that addressed different topics. Therefore when the web was developed and these boards turned into forums there were a variety of different topics right from day one.
These days there are boards that cover topics that you would never dream of. Some of the boards are fairly general in the topics that are discussed while others focus on very tight niches. In general people seem to prefer the forums that have tight niches. This ensures that all of the people who are participating on the forum have an interest in the subject being discussed. This tends to result in the discussion going to a much deeper level. It also tends to limit the number of beginners on the site who ask basic questions.
Because of the fact that there are so many different topics for forums it is important that you make sure that you find the right forum if you have something that you want to discuss. Nothing will irritate people more than people asking questions that are unrelated to the topic of the forum. This can be tricky in some cases. For example if you are looking to discuss IT you will likely find that the forums are further broken down into very narrow topics. This can make it hard for the beginner to determine which forum they should be using. The best thing is to read several of the posts to get an idea of what topics are being discussed before you start to contribute.