A DataItem part specializes a primitive data type by assigning it a name and optionally limiting the values that can be assigned to it. For more information, see "Specializing primitive types as DataItem parts."
After you define a data item, you can specify the data item name as the type of a variable in a logic or Record part, a parameter in a function or called program, or a column in a data table. You can use a data item variable anywhere that you can use a variable based on the same primitive data type as the data item. For example, if you create a data item based on the FLOAT primitive type, you can use the data item anywhere you can use a FLOAT.