C# is a robust and easy-to-learn Object Oriented Programming (OOP) language designed by Microsoft. C# fits the Common Language Infrastructure (CLI) open specification. If you do the research, you will discover that C# is very similar conceptually to C and C++ and is also very similar to Java.

To begin to understand OOP, we must understand that these programs are built out of collections of data structures and functions called classes. A class is the blueprint from which we make an object.

Classes can be something as simple as a cup or as complex as a Tesla Model X, though generally the more complex an object, the more objects that are involved. For instance, a car object would be made up of a chassis object, an engine object, door objects, and so on. Integrating these objects together with their functions would result in a complete car.

Objects use actions or functions to interact with each other. These are referred to as methods. With our Cup.cs class in mind, let's assume we have two other classes, fluid.cs and hardwoodfloor.cs. In OOP, we could write a method of the cup class called SpillCup. This function could pass a copy of the Fluid object to the Hardwoodfloor object.