What does "Most Active Person" mean?
Most Active Person is a system standard field that shows as a header field for organizations. It is determined by the Person (excluding teammates, but including people external to the organization) that is associated with the most Messages, Incidents (if there's an active Help Desk integration), and Notes for the organization within the three months before Last Contact. Currently, it does not consider the number of Documents.
Last Contact is another system standard field that is the date of the latest Message, Incident (if there's an active Help Desk integration), or Note.