The References ability hosts references used in other abilities within MacPractice.
Generally, Reference records can be added to the References Ability with the sidebar plus button, then selected within corresponding menus or used as filters within Reports. For example, records added to the Payment Type Reference node can be selected as payment types in a patient's Ledger, then tracked through the Daily Posted/Procedure Date Day sheet or Gross Receipts Reports.
References are often used within specific tasks and may be added directly through the related Ability rather than the References ability. Likewise, the documentation for using a specific Reference may be within the guide to that Ability.
Information on the Plans tab inside the Insurance Company Reference can be found Here.