!Field
ID is an numeric field that uniquely identifies a record within the data base.  This uniqueness of this field is automatically maintained through [data base sequences] and [data base triggers].  

It is through ID and [foreign key] links to this field from other tables that records are linked through the data base, and by which [referential integrity] is maintained.
!Domain
ID is also an [application domain|DOMAIN] which imparts the following characteristics:
* Oracle data type is [NUMBER](10)