Do you wish that sometimes you didn't have to receive every reply to a discussion that doesn't concern or interest you? With email subscription, you can do just that. If you've set up your email notifications (see blog post) to alert you to new topics posted in the forum, you'll get a single email notifying you of the new discussion. Do nothing and you won't get another email regarding the topic. However, if a topic is of interest to you and you'd like to read each posting in that thread, you can enable email subscription to that thread. At the top of the discussion you'll see a button that says "Enable Email Subscription" (See below).
Click that and it changes to
You have now subscribed to the thread and you'll be emailed each time a new posting is made in that discussion ONLY. Change your mind? Go back to the discussion and click the disable button and notifications stop.