Subscription - you will get email notifications about new activities in the forum.

1. You can be notified when new postings are created in the forum by "Subscribe for new topics"

2. As a creator of the post, you can be notified whenever there are replies to your posting by "Subscribe for new replies" 

3. You can "unsubscribe" anytime if you want to either your own post's replies or the entire forum.

4. By default, when you are creating a topic, you will be subscribed automatically for the replies. You can uncheck if you want.