10 Things You Need to Know about Relationships in Access 2013
Set cascade update related fields in the Edit Relationships dialog to update the key value in the child table when it’s updated in the parent table.
Suppose you have two tables, a list of categories in an ExpenseType table (field name Category) and a field in an Expenses table called Category. The Category field in Expenses is populated by a combo box that pulls its data from the ExpenseType table’s Category field.
Further suppose that a typo was made for Dining, it was spelled Dinning. If you’d set cascade update related fields, you can edit Dinning in ExpenseType to Dining and it will change on every record where used in the Expenses table.