Here is an understandable article about how to put together a normalized database.
One topic covered is what should be used for a Primary or foreign key.
"In general, a key field should have these characteristics:
Should be One Field
It is possible to define multiple fields as the key fields of a table, but a single field is preferable. ...Far better to have a CustomerID number than a combination of other fields to define a customer.
Should be Numeric
Access offers an AutoNumber field that is a Long Integer which is ideal for key fields. These values are automatically unique for each record and supports multi-user data entry as well.
Should Not Change Over Time
A key field should not change over time. Once identified, like a social security number, it should never change.
Should be Meaningless
To ensure a key field doesn’t change over time, it should have no meaning and therefore no reason to change over time.