Like most ERP systems, Odoo has specific database requirements: in this case, PostgreSQL. PostgreSQL is an open source, cross-platform Object Relational Database Management System (ORDMS). While not popular on the scale of Microsoft SQL Server or MySQL, PostgreSQL is an enterprise-class database server with many advanced features. In fact, PostgreSQL stacks up very well against far more expensive databases such as Microsoft SQL Server and Oracle Database.

PostgreSQL runs on every major operating system. For most Odoo installations, Ubuntu is the operating system of choice. However, PostgreSQL will also run quite well under other versions of Linux, Microsoft Windows, and even Mac OS X.

You can learn more about PostgreSQL at http://www.postgresql.org/.