Difference between Database character set & National Character Set..?

Hi..,
What is the difference between Database character set & National Character Set..?
I think if I use the Database character set as Unicode (AL32UTF8) it accepts the data in any language..
but what is National Character Set ?

Thanks in Advance
Giri K.Y.

http://download.oracle.com/docs/cd/B....htm#sthref146