C# allows you to create new types. There are five kinds of types that you can define.
A class is a data structure containing data and its associated behavior. You can create an instance of a class using the new keyword, giving you an object.
A struct is similar to a class, containing data and behavior. But an instance of a struct is created on the stack, rather than the heap.
An interface defines a set of methods, properties and events that a class can implement. It is just a description of what a class needs to implement, in order to fully implement the interface.
A delegate is a definition of a method signature, which includes the data type of the method’s parameters and return value. An instance of a delegate type references a specific method.
An enum type represents a set of named constants.