When you post in Forums, you'll have the option of posting as a discussion or a question.
Discussions
When you choose to post a discussion, you'll begin a thread that has basic options. Members can reply, like, share, and elect to be notified on any replies.
Questions
When you choose to post a question, you'll launch a thread with functionality that is slightly more robust than a simple discussion. As with discussions, members will be able to like, share, and subscribe to replies. In addition, if a member posts a response, they can click the suggest as answer box to indicate confidence in the accuracy of their response. The author of the question can then verify the suggested answer or mark it as a response only.
One more feature: by clicking "I have this question too", a member will be able to see this question on the Question tab of their profile page. The number next to the "I have this question too" button shows how many and which members also had that question.
Change a Post from Discussion to Question, or Question to Discussion
You can change your post from a discussion to a question by clicking Edit (sometimes under the More menu) and selecting Question or Discussion at the top of the post. Only the author of a post has the edit permissions to do this.
