Many kaizen programs aim to have a continuous flow, which means processes are constantly moving without interruptions. This is also the ultimate goal of lean production. A "cell" is a group of devices that perform tasks in a certain order, but it is not often to find a smooth and uninterrupted process, which is what makes a cell.
In an ideal world, the product would flow smoothly from the beginning to the end, reaching the customer through all the stages of its production. But that would be too much to handle all at once. We need a place where we can focus. That place uses a system called a "pacemaker".