Storyline Streaming

Can anyone tell me exactly how SL streams content?  I think that I read somewhere years ago (possibly when Publisher was new) that whilst the user is viewing one piece of content the next piece of content is being downloaded.

I am wanting to include a large video in a project so am planning to cut the video up into smaller segments to facilitate streaming on the assumption that the above is correct.

If I am right, is this streaming done on a slide by slide basis?  Or can I put the pieces of video in separate layers and push from one to the other, all on the one slide?

Hope that makes sense?