Relational Databases are made up of multiple linked tables. They employ a design where each table collects a minimum of duplicative data. The principle behind a relational database is a design where changing one piece of data automatically makes changes everywhere else. The Relational Database design makes it easier to handle the everyday managing of the data (you do not need to copy and paste the information in multiple places).
To understand how a Relational Database works, you might want to become familiar with the concept of Third Normal Form.
For an example of how to create tables for such a database, see the tutorial on the Creating a Database Example page.