C#.Net Basics: What is class? How to Declare a Class?

• A class is a construct that enables you to create your own custom types by grouping together variables of other types, methods and Events.
• A class is like a blueprint. It defines the data and behavior of a type.
• If the class is not declared as static, client code can use it by creating objects or instances which are assigned to a variable.
• The variable remains in memory until all references to it go out of scope. At that time, the CLR marks it as eligible for garbage collection.
• If the class is declared as static, then only one copy exists in memory and client code can only access it through the class itself, not an instance variable. 
• Unlike  structs Classes support inheritance , a fundamental characteristic of object-oriented programming.
• Classes are declared by using the class keyword,
• The class keyword is preceded by the access level. The name of the class follows the class keyword.
• The remainder of the definition is the class body, where the behavior and data are defined.
• Fields, properties, methods, and events on a class are collectively referred to as class members.

             Access level class Customer

  {

    //Fields, properties, methods and events go here...

  }

 http://msdn.microsoft.com/en-us/library/x9afc042.aspx