C# is a programming language developed by Microsoft. The current release at the time of writing this book is C# 7.0. The language appeared in 2002. This language is an object-oriented language and component-oriented. The current version has various new features such as ValueTuple, Deconstructors, pattern matching, the switch statement local function, and so on.
We are not going into details of these features as it's beyond the scope of this book. Refer to https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/ for more details.