SharePoint Developer Question:

LINQ is a feature of the programming languages C# 3.0 and Visual Basic .NET. LINQ allows the user to query in an object-oriented way, supports compile-time check, gives the user 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. Hence, developers may find that it is the only query syntax that they ever need to know. It is commonly used to query objects collections, XML and SQL server data sources.

LINQ to SharePoint is officially being supported with the 2010 release.It works similar to LINQ to SQL or LINQ to Entity.
The LINQ to SharePoint Provider is defined in the Microsoft.SharePoint.Linq namespace. It translates LINQ queries into Collaborative Application Markup Language (CAML) queries.The gateway class for the LINQ to SharePoint provider is Microsoft SharePoint.Linq.DataContext which represents the data of a SharePoint Foundation Web site