SQLite
SQLite (pronounced ess-kue-ELL-ite, like a type of rock) is a lightweight RDBMS (relational database management system) that uses SQL (Structured Query Language). It can add high-performance database functionality to an application, without the overhead of a traditional database system.
Unlike client-server database systems, such as MySQL and PostgreSQL, SQLite does not run as a separate process. Instead, it is provided as a library that is linked to the application software. The SQLite library is written in C, with bindings that allow it to be used by other programming languages.
SQLite was released on August 17, 2000 by its developer, D. Richard Hipp. Today, it's used in many software applications, including Chrome, Safari, Firefox, Laravel, Django, WordPress, Evernote, and Skype.
The source code of SQLite is published in the public domain, meaning it's not subject to Copyright, and anyone can use it for any purpose.