This document provides an introduction to relational databases. It defines key concepts such as what a database is, how data is organized into relations and tables, what a relational database is, and what a database management system (DBMS) is and does. A DBMS allows users to create, update, query and manage the data and relations within a database through the use of database queries and commands. It also enforces integrity rules and authorization controls on the data. Relational databases organize data into logical relations, and relations can be represented visually as tables but the logical relation does not depend on how the table is structured or ordered.