In the web hosting world, certain database software is commonplace. Most system administrators, even the new ones, have heard of MySQL, MSSQL, and/or PostgreSQL. Using SQL databases typically requires a database server to be running on the system. MySQL, for example, runs as a service in Linux called mysqld, or something similar. An alternative to running these types of services is to use SQLite.
Because it does not run via a sever, SQLite does not require the configuration and maintenance of other database systems. As a result, it is considered light and easy to use. Rather than running on a server, the database code is linked directly with the software using it. The library itself is small and can be installed in smaller installations.
According to their website, SQLite is the most often deployed database engine used in many web applications. It is free and open source, without a license, released into the public domain. You can download the libraries at the SQLite website.