This document discusses databases and SQL. It defines a database as an integrated collection of data managed by a database management system (DBMS) using SQL. The most popular type is the relational database which organizes data into tables related through primary keys. SQL is used for queries with statements like SELECT, INSERT, DELETE, and UPDATE. Database interfaces like Perl DBI, PHP dbx, and Python DB-API allow access from programming languages. ADO.NET is an API for database access in .NET.