Included Persons is used to record the details of all persons associated with a Note, not only those individuals that are being researched or listed on a Family File, e.g. A witness to a marriage, the doctor on a convict ship, etc.
Included persons is an extremely useful tool for tracking and analysing information for aspects such as:
Finding people having similar names
Attendance of people at events and the roles they played at those events
Confirming ages of perople through the events in their life