What is const object and const function

class CWnd
{
public:
    void ConstFunction() const
    {
        // It's a const function, you can change the member of this pointer.
    }

    void UnConstFunction()
    {
    }
}

// It's a const object, you can't change the member of wnd, you can't call the un-const function of 
// CWnd, such as UnConstFunction.
const CWnd wnd;