In a relational database, tables store the data. Each table comprises a number of columns of a particular data type. Information is stored in rows of the table. Finally, tables can be related to other tables, using primary and foreign keys to map the rows in one table to rows in another.
The database in Force.com, on the other hand, uses objects to store data. Objects contain the functionality you expect in a table and more, but you should be aware that the difference also points to a difference in functionality. The object comprises a number of fields. Objects can be related to other objects, with relationship fields mapping records in one object to records in another. All attributes of an object are described with metadata, outlined later. Information is stored in records of the object.
When an object is materialized in the Apex language, it is called an sObject, to differentiate them from instances of Apex classes. We’ll use this terminology throughout the article.