This following Points are taken from Salesforce user guide how different field type values And the field accessibility are imported:
Field accessibility:
- New values for picklists: If you import the data to any picklist field, the wizard warns you when you attempt to load a value that does not match any existing picklist value. If you ignore the warning, the value gets automatically added to the imported record. Your administrator can later add this value to the picklist field.
- Multiselect picklists: To import values into this field, separate values by a semicolon in the import file.
- Checkboxes: Use 1 for checked and 0 for unchecked values in the import file.
- Default values: For the picklist, multiselect picklist, and checkbox fields, the default value gets automatically populated in the new or updated record, if the field is not mapped in the Import wizard.
- Date/time fields: Ensure that the format of any date/time field that you are importing matches how they display in Salesforce per your locale setting.
- Formula fields: Don't accept any value in the import as they are derived and read-only.
- Field validation rules: Salesforce runs validation rules on the records prior to importing them. Records that fail are discarded. You may want to deactivate validation rules before running the Import wizard.
Field accessibility:
- In the organization-wide import of accounts and leads, you can import data into any standard or custom field, even if it is hidden or read-only in your page layout or the field-level security settings.
- For the Import My Contacts wizard, you can import data in only those fields that are editable in your page layout or the field-level security settings.
