Users can get points for participating in the community.  Once you post a discussion and someone responds, make sure to reward them by marking their reply as Answered or as Helpful.

Once a user posts a reply to your discussion, you (as the originator of the post) can go back to your post and display all the replies. The responses will be listed below your original post.  Here, you will be given icons in the bottom of each reply that are "Correct Answer" or mark as "Helpful Answer".  You can choose one reply (and only one) as the correct answer and I believe you can choose two replies as helpful.