C++ :: State Design Pattern - Calling A Class Member

In the following code example of the State Design Pattern, in the main code at the bottom it defines an instance of class Machine, and then calls Machine::off;. Why doesn't it instead call fsm.off;?

Machine fsm;

Machine::off;

Then I tried imitating that by adding a class Abba, and then doing:

Abba a;
Abba::DoStuff();

but that didn't work. Why?

Full code example:

// StatePattern.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
using namespace std;
class Machine {
class State *current;

[Code] ....