Calculated Fields are derived from other database fields or settings or are otherwise indirectly associated with the data being reported.
In an Inventory Report/Label the Calculated Fields include fields such as: Price Total, % Profit, and Qty To Order.
In a Sales Transaction report the Line Item Calculated Fields include fields such as: Profit Amount, Adjusted Price, and Selected Price.
Sales Invoice Calculated Fields include fields such as: Day of Week, Profit, and Percent Paid.
The Customer Database report Customer Calculated Fields include fields such as: HasCardOnFile, Customer Name and Phone. Note: Customer Name and Phone are not actually calculated, but are formed by merging smaller fields.
In general, when looking for a field that should be available on a Report/Label form, check both the Standard and Calculated Field Lists.
See:
Edit Field Screen
Edit Field Screen Field Button
Report/Label Editor Contents