In Discussions, subscribing to a Forum, Topic, or Thread is a way to “Tag” an area of interest in that discussion. Subscribing to a Discussion by Forum, Topic, or Thread will send different levels of notifications to the subscriber. Subscribing at the Forum level will allow the subscriber to receive a notification every time someone responds to any part of that Forum (Topic or Thread). Subscribing to a Topic the subscriber will receive a notification every time someone responds to a Thread in that Topic. Subscribing to a Thread will notify a subscriber someone has responded to that Thread.
To Subscribe to a Discussion feed in Brightspace, Select the Communication tab from your course
Select Discussions from the dropdown
Select Subscriptions under the Discussions page
On the Subscriptions page, from the dropdown menu, select the type of Subscriptions you would like to receive notifications on
Select the type of notification you would like to receive