Difference Between Sql Server VARCHAR and NVARCHAR Data Type

Refer this following link

http://sqlhints.com/2011/12/23/difference-between-varchar-and-nvarchar/

http://social.msdn.microsoft.com/Forums/en-US/b6615caa-629b-45ac-9710-aab7f6e172b3/varchar-and-nvarchar-use-what-is-exact-difference-between-these?forum=sqldataaccess