Stream
you can think of an array as a structure that you move past... like one of those fancy old libraries with the moving ladder. You move to the position the data is in, and the data stays put. A stream is more like a conveyer belt. You stay in one place, and the data comes to you. You just control fast it comes. It's a more restricted idea than the array, because with an array you can move backwards and forwards, but a stream can only pause or move forward (or abort)