Read these two web articles and answer these questions:
http://www.opensource.org/docs/definition.php
http://searchenterpriselinux.techtarget.com/originalContent/0,289142,sid39_gci1069685,00.html
* What is an open source database?
* Why would a company want to use an open sourced database?
The solution clearly explains what is a Open Source Database and why a company want to use Open Source Database.