LINQ stands for Language Integrated Query. LINQ is one of Microsoft's most exciting, powerful new development technologies. LINQ is a part of .NET framework 3.5. .NET Language-Integrated Query defines a set of operators that allow data filter and projection operations to be expressed in a direct yet declarative way in any .NET-based programming language. Instead of writing separate queries for getting results from the database, LINQ makes it possible to integrate those queries into the code itself. LINQ implements one kind of query architecture which is used to provide implementations that work on both XML and SQL data. Only with LINQ it is possible to express efficient query behavior in their programming language of choice and transform data results into any required format and then easily manipulate the results.
LINQ is very extensible since the LINQ call is unhooked completely from the source, so updating one file can unhinge existing data source and move it completely without touching any lines of client code.