Live streaming refers to the fact that the response is sent progressively, rather than rails rendering the whole thing in one go and then sending it. This enables some long-polling type features. It can also improve user experience, since you can send the head of the page, telling the browser about what css/javascript to download and have it make a start on downloading them before you've finished sending the response.
There's not really any connection with the streaming of audio/video.
Fred