What does T-SQL string mean by adding N before?

What is the meaning of adding N before the T-SQL string, such as select @ status = N 'stopped ', then why should N be added before the string stopped? In addition, we find that N is not affected in some places, and N must be added in some places. Here, www.2cto.com N indicates Unicode, which is a double byte character. For Western characters, one byte is enough. For Eastern characters, two bytes are required for storage. To ensure consistency, standardization, convenience, and compatibility, Unicode requires that Spanish characters are also stored in two bytes. That is to say, adding N indicates that the string is stored in Unicode mode. But what is the reason for the same addition and not addition? This is caused by automatic conversion. For example, declare @ status nvarchar (20) select @ status = n' stopped 'select @ status = 'stopped '. In fact, the values of the preceding two statements are the same, because the variable type is nvarchar (Unicode type ). In some cases (for example, the sp_executesql parameter) cannot be automatically converted, so N is required.