"Good things & impact stories" is for posts that discuss achievements or updates that seem impactful and exciting. 

A broad range of posts could fall under this tag. For example: 

• A retrospective about what led to a success in a certain area
• A list of events or positive trends from the last year, which the author wants to celebrate
• Estimates of the impact of some intervention

For posts that are more focused on intermediate metrics/results (e.g. engagement or other data relevant for an organization's strategy), consider using the organization updates tag.