What is a database schema?

A database schema is a definition for how to organize data within a relational database.  a relational database can also have multiple schemas.  Schemas may also describe the source system the data in that schema comes from.  Schema includes table names, fields, data types, and the relationships between all these items.  Schemas are visually represented using Entity Relationship Diagrams (ERDs), and the process of creating schema definitions is called data modeling.