1. char - is the SQL-92 synonym for character. Data is padded with blanks/spaces to fill the field size. Fixed length data type.
2. nchar - is the SQL-92 synonym for national char and national character. Fixed length data type.
3. varchar - is the SQL-92 synonym for character varying. Variable length data type.
4. nvarchar - is the SQL-92 synonym for national char varying and national character varying. Variable length data type.