It's simply declaring the string as nvarchar data type, rather than varchar.
You may have seen Transact-SQL code that passes strings around using an N prefix. This denotes that the subsequent string is in Unicode (the N actually stands for National language character set). Which means that you are passing an NCHAR, NVARCHAR or NTEXT value, as opposed to CHAR, VARCHAR or TEXT.
To quote from Microsoft:
Prefix Unicode character string constants with the letter N. Without the N prefix, the string is converted to the default code page of the database. This default code page may not recognize certain characters.
varchar: Variable-length, non-Unicode character data. The database collation decides which code page the data is stored using.
nvarchar: Variable-length Unicode character data. It depends on the database collation for comparisons.
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