Basically a "Message Board" and the term "Forum" are the same thing. It is a community site where you can go to see what others are talking (typing) about. You can join in on the topics discussed, give views, opinions, post pictures, link to other sites, tell stories and in general just have a good time.
What makes a good board is the discussions there and the input and views of the people there. It is what you make of it and you are encouraged to become a member and join the fun.
It is absolute free to join the Message Boards and it is safe to be there, If you have any trouble or see questionable statements of rudeness or vulgar language just let one of the "Moderators" know and it will be taken care of as soon as possible (removed) and the person warned.
If there is this type of behavior and the person has been warned and continues this type of behavior, they themselves will be removed.