LINQ to SQL is an ORM tool that connects to SQL Server databases. It generates business objects to match a database's table structures, which are all centrally available through the DataContext class. The LINQ-to-SQL designer creates a custom DataContext class that contains a series of Table<Entity> objects representing each of the tables in your database.

LINQ to SQL makes it easier to create application architecture, with some caveats (what doesn't have any in life?).