What makes Lean different is the basic understanding about the consumer demand for a product or service and how to respond accordingly.
With it's origins in early modern industrial companies (The Ford Motor Company being the exemplar of this early type of organization) Push is about the ability of large corporations and organizations to accurately predict and mold demand of customers and then organize their operations around those predictions in order to sell those products.
Here is a highly stylized automotive manufacturing assembly line to illustrate the traditional Push-based factory:
Pull identifies and responds to needs and demands for an organization's products and services by "pulling" directly from the customers and potential customers. In a reversal of Push, the Lean organization starts with the end customer and using Kanban scheduling system for later steps in the assembly line to signal an early step for material. Nothing is manufactured or produced unless a Red Kanban Card is indicated by the next step in the assembly line.
We now use the same three steps in the Push example to show how Pull processes are different.