What is the National Character Set ( ORACLE )?

What is the National Character Set?
The National Character set (NLS_NCHAR_CHARACTERSET) is a character set which is defined in addition to the (normal) database character set and is used for data stored in NCHAR, NVARCHAR2 and NCLOB columns. You can find your current value for the NLS_NCHAR_CHARACTERSET with the following select statement:
SQL> select value from NLS_DATABASE_PARAMETERS where parameter = ‘NLS_NCHAR_CHARACTERSET’;