[DB-SIG] a simple question on rdbms and berkeley db

[ali]

a simple question on rdbms and berkeley db....

i needed a database for a simple message board that i am creating using
python... then there was a question on databases??? i first considered
firebird and was actually working well... and i came across berkely db...
and i really got confused...

my question is, what is the difference between rdbms and berkeley db or even
gdb and others of the same genre???

another question, in my simple web-based message board?? what database is
the most appropriate??

or am i wrong in assuming they are different...

i'm new to databases, please be gentle with me... :)

thanks...
ali