Subforms are useful for displaying information from two different tables or queries, where many records in one table (displayed in the subform) are associated with one record in another table (displayed in the master form).
The LinkMasterFields and LinkChildFields properties of the subform control are used to choose the records in the subform appropriate for each record in the master form. Whenever any of the LinkMasterFields is changed, Microsoft Access automatically re-queries the subform.