Missions define the sets of activities you want users to complete in the community, and the associated rewards.

A mission contains the following elements, each of which has its own tab: A set of default missions consisting of typical community activities is included in Gamification. You can use these missions as is, modify them, or create your own. Note that any missions that are enabled in the Gamification Console will be visible to users as soon as Gamification goes live in your community.
Note: You'll see the word Challenges as well as the word Missions in the interface. They're the same thing.