What happens if I select the "Overwrite record(s)" option during restore?

If the admin chooses to overwrite the Salesforce records, the existing version will be deleted, and the record will be restored with the version available in the backup snapshot. By choosing to overwrite the record, not only do the deleted records get restored but also the ones that have been modified will roll back to the point in time given in the backup snapshot.  

If the admin does not choose to overwrite the Salesforce records, the record will be restored with a new ID.