hooby,
An AutoNumber is just a unique # that Access provides to
identify a record. It won't "mean anything" to the user,
they may or may not be displayed, and they can not be
edited.
They can't be used like serial numbers, because "gaps"
may occur due to record deletions, etc. If you need
serialized numbers, you'll have to do it yourself.
They make joining tables easier, because you just link
the tables on the one field as opposed to multiple
fields like Country --> State --> City.
Wayne