Elsner,
Those darned things are AutoNumbers. Every record in a table should
have a unique identifying number. For some tables that's easy; a
social security number, drivers license, etc.
When you make a new table in Access you should define a unique primary
key. If you don't, Access will offer to supply an AutoNumber field
named "ID". This is a good thing.
For instance, in a database containing people's names, you should
still use the AutoNumber field and use that as the "link" to their
other related information. This ID is unique to them and will never
change, even though their name (first and/or last) may change. It's
a good practice to use these identifying numbers.
As you can see, Access will do all the work of assigning them, all
you have to do is use them to relate info in other tables. You don't
even have to display them, they're only used to ID the record. They
don't even have to be sequential, they can be assigned randomly. They
don't have a "meaning", they're just for ID purposes.
Wayne