The document discusses database management systems (DBMS). It provides examples of DBMS applications like library systems, ATMs, and inventory systems. It explains that DBMSs organize data internally in relational, network, flat, or hierarchical structures. Queries to a database use a structured query language (SQL) to retrieve specific records by fields. Entities in a database represent real-world objects and are characterized by their attributes and primary keys. Relationships associate instances of different entity types that are relevant to an organization.