What does N' stands for in a SQL script ? (the one used before characters in insert script)

I generated an sql script like this,

INSERT [dbo].[TableName] ([Sno], [Name], [EmployeeId], [ProjectId], [Experience]) 
VALUES (1, N'Dave', N'ESD157', N'FD080', 7)

I wonder whats that N' exactly mean and whats its purpose here.

NOTE: By searching for the answer all i can get is that N' is a prefix for National language standard and its for using unicode data. But honestly i am not able to get a clear idea about the exact operation of N' here. I'd appreciate your help and please make it in more of an understandable way. Thanks in advance.