This document explains database and data modelling concepts, covering file-based systems, DBMS features, and relational database design. It introduces entities, attributes, keys, indexing, and referential integrity. It also explains normalization (1NF, 2NF, 3NF), SQL Data Definition Language (DDL) for creating/modifying structures, and Data Manipulation Language (DML) for querying, inserting, updating, and deleting records.