Difference between 2 ways of creating instance.

What difference between this:

 public MyClass class;
    class = new MyClass(); // first variant
    class = MyClass.Instance; // second variant

the second is not a way to create an instance until Instance is declared explicity in MyClass. E.g. this way:

public class MyClass {
   public static Instance { get{ return new MyClass(); }}
}

But usually it is used not this way but to implement Singleton pattern