The question's a bit vague. RDBMS=Relational Database Management System which comprises a number of tables that contain related information and a whole stack of software (the Management System) that manages the data. Probably what you need is a book on Databases.
Alternatively you could download Oracle ( http://www.oracle.com/technology/sof...ase/index.html
) and have a look through the documentation ( http://www.oracle.com/technology/doc.../database.html
) starting with the Concepts manual ( http://download.oracle.com/docs/cd/B...b28318/toc.htm
). Concepts will (eventually) answer your questions.