Introduction to LINQ

Brief explanation take from: Code Digest

Language Integrated Query (LINQ) is a query syntax that defines a set of
query operators that allow traversal, filter, and projection operations to be
expressed in a declarative way in any .NET-based programming language. It
provides a unified programming model for querying and updating data from
different types of data sources and extends data capabilities directly into the
C# and Visual Basic languages. LINQ simplifies the interaction between
object-oriented programming and relational data by applying the principles of
object-oriented programming to relational data.

With the advent of LINQ, a ground-breaking, new concept of a query has
been introduced as a first-class language construct in C# and Visual
Basic. LINQ simplifies the way you work with data queries. LINQ offers you
a unified, declarative syntax model to query any data source including an XML
document, SQL database, an ADO.NET Dataset, an in-memory collection, or any
other remote or local data source that chooses to support LINQ Language
Integrated Queries are strongly typed and designer tools can be used to
create object-relational mappings. It is easier now for developers to catch many
errors during compile-time; also supports Intellisense and debugging.