The lecture explains why entity-relationship (or E-R) models are used, and gives a high-level view of the development process for a database. It describes the database development process as logically parallel to the development process of an application, such as an information system, that uses a database. The development cycle for the application includes requirements analysis, design, and implementation. The development cycle for databases are similar, having a corresponding requirements analysis phase (called the conceptual schema) that is a technical specification of the database requirements. A popular representation of the conceptual schema is an E-R model.