Well, it was designed to help the non-elected branches to communicate data better within itself, and was originally conceived as ARPANET, at least within the US. There was some testing done overseas with it, but, again, it was developed more for military purposes to speed up the rate at which intelligence gathered through espionage got to the necessary people.
Or its purpose is just to help us achieve the answer to the ultimate question of life, the universe, and everything, and whether or not it is really 42. ;)