You can upload any content to the document library - it can be any type of file. There are also plugins available (for example) for embedding flash video or video on a page - they can also come from external locations, but not necessary.
The portal itself is agnostic: it simply generates HTML, so everything that you can generate in HTML is supported (and links to files: images, css, video, audio, etc.). There is no specialized "streaming server" that provides large multimedia files in pieces or in part, but you can still embed them by referencing an external streaming server (if this is what you need, streaming media is not the main task of the portal)
In order to link to such content from the CMS, it usually pays to take a look at the structures and patterns. This will help you separate media links from generated HTML.