The Recent Activity log tracks ALL the changes and meta-data associated with creating, reviewing and validating a damage report.  All additions, edits and deletions are captured in this field.  This allows administrators to track down exactly who worked/touched each assessment. You can filter the activity/changes to each entry based on the level of importance of the changes.  This is mostly used so that you filter for the highlights without being bogged down with every single change to the entry.