Merchant 101 

Overview
Visa & MasterCard are associations of banks. They designed the Electronic payment system for merchants to collect money from customers. The "Players" in this world are: Associations, Issuers, Merchants and Consumers.

There are two graphics below that demonstrate how the system works.

The first one below provides an overview of how the "Players" interact.

This graphic shows "How it Works" on the merchant level.