FireBird is a database system that has been used in many projects. It has nothing to do with Firefox or any browser or email client. Just go to the website to check it out
From the website:
Firebird 2.0 is the happy culmination of more than two years' efforts from a broad-ranging, truly international community of dedicated developers and supporters. It brings with it a large collection of long-awaited enhancements that significantly improve performance, security and support for international languages and realise some desirable new SQL language features. Under the surface, it also provides a much more robust code platform from which the re-architecting planned for Firebird 3.0 is proceeding.