differences between varchar and nvarchar?

Varchar means variable characters and it is used to store non-unicode characters. It will allocate the memory based on number characters inserted. Suppose if we declared varchar(50) it will allocates memory of 0 characters at the time of declaration. Once we declare varchar(50) and insert only 10 characters of word it will allocate memory for only 10 characters.

nvarchar datatype same as varchar datatype but only difference nvarchar is used to store Unicode characters and it allows you to store multiple languages in database. nvarchar datatype will take twice as much space to store extended set of characters as required by other languages.

So if we are not using other languages then it's better to use varchar datatype instead of nvarchar