What do you understand by LINQ?

Language Integrated Query (LINQ) is the collection of standard query operators that adds query facilities into .NET framework languages like C#, VB.NET, etc. LINQ also represents the set of method names with the translation rules that can be used by the compiler for converting fluent-style query expressions into expressions that uses these method names, anonymous types and lambda expressions. LINQ can be used to extract data from arrays, XML documents, relational databases and other third-party data sources.
The LINQ is of the following types:

• LINQ to objects refers to the use of LINQ queries without the use of an intermediate LINQ provider such as LINQ to SQL. 
• LINQ to XML which was formerly known as XLINQ
• LINQ to SQL which was formerly known as DLINQ
• LINQ to Datasets
• LINQ to Entities