What is LINQ in C#?

LINQ (Language Integrated Query) is a set of features in C# that provides a consistent, SQL-like syntax for querying and transforming data from various sources (collections, XML, databases, APIs) directly in C# code. Two syntax forms: Query syntax: var result = from p in people where p.Age > 18 orderby p.Name select p.Name;. Method syntax (fluent): var result = people.Where(p => p.Age > 18).OrderBy(p => p.Name).Select(p => p.Name);. Common LINQ operators: Where (filter), Select (transform/project), OrderBy/OrderByDescending, GroupBy, Join, First/FirstOrDefault, Any/All, Count, Sum/Average/Min/Max, Take/Skip, Distinct, SelectMany (flatten). LINQ uses deferred execution — queries are not evaluated until iterated. Call ToList() or ToArray() to force immediate execution.