phpFox provides tools for you to encourage your users to do more actions on the community. That's the activity points system. You can fully customize the points your users receive on each action from inviting, commenting to creating a new item. You can also configure the conversion rate to convert the activity points to real money. Thus, there are many ways to use this system efficiently, such as promote some active users to be a moderator of the site, give money back to some active users, give awards to users whose points over a limitation.
In user group settings of each app, there is a place to configure the number of activity points your users will receive when creating a new item. Therefore, it's very convenient to lead the focus of your community to a topic you want by giving more points than the other ones.