Alexander´s attempt to make his empire secure helped the Hellenistic Age by spreading Greek culture in a very large area. Alexander's rule led to exchange and blend of culture which meant a lot of changes in geography. This was the Hellenistic Age.
The Hellenistic Age is justified by the extent of the Hellenic culture in ancient period for the European and near Asian areas, due to the Greek political presence after Alexander's conquests, but also to a new wave of Greek colonization.
The Hellenistic Period (politically) is characterized by a division from Alexander's former empire.