Basicly the quilt gets rolled into the throat space as you finish quilting one area. The backing/batting/top start at one end of the machine (outside the throat space ) and get rolled as you advance into the throat space. On smaller machines the quilt roll takes up the room and you have less space to move your machine. Here's a picture of my current machine, the horizontal long area, front to back is the throat space (18'on mine). There are youtube videos on quilting that probably would explain all this better than I can.