The last achievement you earned is shown next to your username in the forum.
Some achievements are rewarded automatically. For example when you have replied to a forum thread you get the Active Member achievement and 100 points.
Other achievements are awarded by admins and moderators directly. For example if you answer the six questions for the Prepper Profile achievement, an admin or moderator will send you the Prepper Profile badge and 300 points.
A list of different achievements can be found below. In the future we plan to have special promotions and a private section only visible for senior members.