The Parameters panel displays all Parameters configured for the print layout.
Clicking the Add Parameter 
button opens the Add Parameter dialog. In the dialog you will see the following properties:
▪Name: The name assigned to the parameter.
▪Description: A description of the parameter.
▪Type: The data type expected as input. If using an OBJECTID field as your input, this should be set to Number (32 bit integer).
▪Visible: Determines whether the parameter is visible in the client application running the report.
▪Multi-Value: When enabled, this property allows multiple values to be passed to the parameter.
▪Allow Null: Determines whether null values can be passed as an input.
▪Expression: An optional expression used to set a Value.
▪Value: Provides a pre-defined value or values to be used when running a print template.
See also...
