Discussions are used to facilitate unstructured work, allowing multiple people to interact “chat style” about a particular topic.
Common topics are: Teams, Service Requests, and Tasks.
You can invite others (internal or external) to participate in a discussion. If you are not actively in a discussion when activity takes place, you will be kept informed by occasional emails and digest emails of the discussion.
Some of the great benefits of discussions:
If you have a specific task or approval to assign, particularly one with a specific due date, you'd want to use a subtask. However, if you
you will want to use a discussion. There are even more applicable use cases, but these are a few you are likely to run across.
When in a discussion, you add a comment to it in the bar down at the bottom of the screen. On the left side of that bar is a menu with two icons. The paperclip lets you add attachments and the plus sign lets you invite people. Anyone with an email can be invited.