As fore mentioned, LINQ is a functional programming model, consists of syntax in languages and APIs in libraries:
Object-oriented programming and functional programming are programming paradigms. A programming paradigm is a fundamental style or approach of programming. Paradigms are not mutually exclusive. It is common for one programming language to support multiple paradigms, and C# is such a language.
C# is a functional and object-oriented programming language built by Microsoft. C# works with a family of programming frameworks crossing many platforms and devices. C# has been used by millions of people to build applications, services, mobile apps, and games, etc.