Open manage | Database | Fields and double click any existing field definition to bring up the field options dialog.
Click the auto-enter tab and look at all the auto-enter options that are possible.
If you enable this option, all such defined options for all the fields in the target table will be applied to each record during import.
If you have a field defined to auto-enter serial numbers in your target table, each newly imported record will be assigned a new serial number in that field.
auto-enter calculations, creation/modification dates, etc all get applied during the import.
This can be a very good or very bad thing depending on your data and the design of your table.
If you choose to import contact data into one of the contact tables in one of the starter solutions, this is an option you must select or the new contact records produced by the import will not have a a contactID number that is required in order for many of the scripts in these starter solutions to work correctly.