LINQ is a feature of the programming languages C# 3.0 and Visual Basic .NET. LINQ allows you to query in an object-oriented way, supports compile-time check, gives you intellisense support in Visual Studio and defines a unified, SQL like syntax to query any data source. But unlike other languages and query syntaxes which vary from one type of data source to another, LINQ can be used to query, in principle, any data source whatsoever. It is commonly used to query objects collections, XML and SQL server data sources.The LINQ to SharePoint Provider is defined in the Microsoft.SharePoint.Linq namespace. It translates LINQ queries into Collaborative Application Markup Language (CAML) queries.