In Discussions, you can subscribe to a Forum, Topic, or Thread, as a way to get notifications to an area of interest in that discussion.
To subscribe to a Forum
If you subscribe to a Forum, you will receive a notification every time someone creates something in that forum (new topics, new threads, new responses).
Click the Actions dropdown menu near the Forum title and select Subscribe.

To subscribe to a Discussion topic
If you subscribe to a Discussion topic, you will receive a notification every time someone creates a new thread or respond to a thread in that topic.
To subscribe to a Discussion topic, click Subscribe underneath the topic title once you opened it up.

To subscribe to a Thread
If you subscribe to a Thread, you will receive a notification every time someone creates a new thread or respond to a thread in that topic.
To subscribe to a Thread, click on Subscribe underneath that Thread's title.

You can then chose which type of notification you would like to receive and then click Subscribe.

To check or change your subscriptions
Go to Discussions List (Click Activities > Discussions).
At the top, click the Subscriptions Tab.
You will see the list of all you subscriptions, and you can also edit them.
