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.

Here's a quote from Oracle's metalink Note:276914.1 The National Character Set 
in Oracle 9i and 10g:

  "1) What is the National Character Set?
   
      The NLS_CHARACTERSET is used for CHAR, VARCHAR2, CLOB columns;
      The NLS_NCHAR_CHARACTERSET is used for NCHAR, NVARCHAR2, NCLOB columns.
   
      NLS_NCHAR_CHARACTERSET is defined when the database is created 
      and specified with the CREATE DATABASE command.
      The NLS_NCHAR_CHARACTERSET defaults to AL16UTF16 if nothing is 
      specified."

HTH,
- Vitaliy