Static classes and class members are used to create data and functions that can be accessed without creating an instance of the class.
Static class members can be used to separate data and behavior that is independent of any object identity: the data and functions do not change regardless of what happens to the object.
The main features of a static class are:
They only contain static members.
They cannot be instantiated.
They are sealed.
They cannot contain Instance Constructors (C# Programming Guide).