Schema includes the tables, relationships, domains and business rules associated with a specific dbms. For example, when creating a table in Access where all business rules associated with data in that table are included, we would have a specific schema. It is a view of that database from the outside by a dba or other humna

Subschema is the view of a database as it appears to a specific application program. Is only a subset of the database and is very specific to the application being processed.

Want to understand both the entire database as a whole as well as which portions of a database a specific application program will affect.