There are various different names for an internet forum.  Some consider it as a message or bulletin board, while others call it a threaded discussion or a discussion group. But what is a forum, you may ask.

 Forum

The crude definition of a forum is a place where people can start discussions, in the form of threads and reply to other people's threads.  A forum’s subject matter can be practically anything and that subject turns the forum members into what is commonly known as an ‘online or virtual community’. A member of the community in the forum creates a thread, which everyone can see.  Once another member sees the thread, they have the option to respond to it, which is also visible to the entire community.  Hence, a discussion is created through forum posts without having all users online, simultaneously.  

Threads 

Forums can be considered as containers for threads started by the members.  Based on the permissions of community members as defined by the forum administrator or forum moderator, they are allowed to post replies to existing threads and start new threads.  In addition to all this, users can even post anonymously (if such a thing is allowed by the (forum administrator) or with their registered username.