The data types in Oracle are Numeric, Varchar, Varchar2, Date, LOB, CLOB and BLOB
Char(20)- This means it takes 20 bytes of storage. Max limit is 20.
Varchar(20)- If you give ‘abcd’ only 4 bytes storage it takes. Max limit is 2000 bytes.
Varchar2- Max limit is 4000 bytes
Char,Varchar and in Varchar2 String is case sensitive.