EssentialPIM all editions use Firebird as database engine. All data (except program settings) are stored in *.epim file, which is a standard Firebird database file.

So, what is a Firebird?

It is an extremely popular, industrial- strength, open-source database engine. It runs on Linux, Windows, and a variety of Unix platforms. Firebird offers excellent concurrency, high performance, and powerful language support for stored procedures and triggers. It has been used in production systems, under a variety of names, since 1981.

What it gives to you as a user?

Open- source- it means all your data is accessible using standard Firebird tools (unless it is encrypted of course and permissions are set).

Firebird is a very popular database engine with an active developers community- it means there are a lot of tools for backup, fixing, and managing databases.

Firebird has been used and developed since 1981- it means an extreme stability, integrity and speed.

For more on Firebird, visit: http://www.firebirdsql.org/, http://en.wikipedia.org/wiki/Firebird_(database_server)

For utilities for Firebird, visit: Contributed Downloads