A value stream is the series of activities that take a product from the supplier to the customer (for a physical product), or from the customer request to filling that need (for a service or informational product). It includes all the value-adding processes that the company performs in the Lean office or on the shop floor.
The value stream takes a big picture view of what a company does to deliver goods or services to the customer.
The value stream is looked at in reverse of the flow of the product. That means identifying waste by starting at the customer and looking upstream.
The value stream is often visually depicted on a value stream map, and has given rise to a new way of running a Lean company. It is now common to see a value stream manager responsible for a product line.