Explain about a supply chain.

A supply chain is a key subsystem of a value chain that focuses primarily on the physical movement of goods and materials along with supporting information flows through the supply production and distribution processes.
Supply chains are all about speed and efficiency; poor supply chain performance can undermine the objectives of the firm and can easily result in loss of customers, either individual consumers or major retailers. As a firm's product lines and markets change or expand, the design or redesign of supply chains becomes a critical issue.