Officially, what is typename for?

Following is the quote from Josuttis book:

The keyword typename was introduced to
specify that the identifier that
follows is a type. Consider the
following example:

template <class T>
Class MyClass
{
  typename T::SubType * ptr;
  ...
};

Here, typename is used to clarify that
SubType is a type of class T. Thus,
ptr is a pointer to the type
T::SubType. Without typename, SubType
would be considered a static member.
Thus

T::SubType * ptr

would be a multiplication of value
SubType of type T with ptr.