What happens when you click on such a link depends entirely on how the manager or administrator has set up the conference. You may have to log in, providing a username and password, or, if you don't yet have an account, you may have to register and provide some basic information about yourself, such as a username, password, and your full name. When you open the conference, you'll probably initially see a list of forums and threads. Remember, forums are like clusters of people talking at a party. Threads are like the conversations they are having, each one with its own starting point.
People enter and exit threads according to their interest in reading or participating.
If you're the quiet type, you can just browse around without any obligation to post messages. What you'll probably do first when you enter a conference is click on a thread that looks interesting so you can read the messages that are inside. However, you may not see any forums or threads at first. You probably only need to set a few conference options before seeing all the forums and threads that are available to you. See Conference Options for information about filtering the display of messages by their age.