The Evolution of the Intranet
If we sum it up succinctly, we could say the intranet as a "system" has progressed from a simple CMS for "internal websites", through more structured "publishing" of news and information, into the collaboration sphere, then into more "social" collaboration, until now with the introduction of terms such as digital workplace when we can say that the intranet is an ecosystem, or a complex system of systems.
As such your intranet may have many constituent parts, a Web Content Management system, a portal platform, a enterprise social business platform, a digital asset management system with internal or externally hosted streaming media servers, web interfaces to document management, ERP, HRM systems, the list goes on……..