What is the difference between the "push" and "pull" methods of material flow? Which method does lean systems use?

What will be an ideal response?

With the pull method, customer demand (an order) activates the production of the goods or services. The production system does not anticipate the need for more product until indicated by a customer order. The push method begins with a production schedule and customer demand is assumed (or hoped for). Lean system processes use the pull method of production.