Video streaming: pushing a swimming pool through a straw.

If someone asked you to move all the water from one swimming pool to another, you would try to use the biggest hose and the most pressure you could find to make the transfer relatively quick and easy. Moving a video file from one computer to another is very similar to moving all that water: there's usually a tremendous amount of data (lots and lots of water) and very little bandwidth (the size of the hose).