Creating Impacts is what we define as "sharing information about what you did in the community that made an impact of some kind." Since for most of the time, the easiest way to quantify impact is service hours, this can be a simple metric used in creating impacts.
In GivePulse, you may create impacts for groups and events of all kinds. On every group and event page, there is a "Add Impact" button that will allow you to input information about your impact.
Groups and event admins may define what is in an impact, e.g., it may be the basic service hours or it can include something more complex like "how many trees did you plant?"
Whatever is requested by admins, when you create impacts, you are sharing information for them to do data analysis on the impact you and others are doing for their cause. Since you are using GivePulse, you may also review, edit and reflect on your own impact over time.