In dimensional modeling it can be very useful to have a durable supernatural key for each record. In contrast to natural keys that come from the source system a supernatural key is stable over time and can be the same for records from different sources (ex. if you have customers in multiple systems,) these properties can be very useful.
In the Jet Data Manager, you can add the supernatural key as a field in a table (right click-> Add Supernatural Key Field):
The supernatural key field gets its value from a key store. When you set up a supernatural key field you select the fields to base the key on (ex. a company name and a zip code.) Jet Data Manager compares these field values to other values in the key store and returns the key that matches. Depending on your needs the supernatural key can be a GUID or an integer.