This document defines and classifies different types of e-commerce. It identifies 14 types including business-to-business (B2B), business-to-consumer (B2C), consumer-to-business (C2B), consumer-to-consumer (C2C), peer-to-peer (P2P), mobile commerce (m-commerce), business-to-employee, e-government, e-learning, and collaborative commerce. For each type, examples are provided of how the transactions occur and common websites that engage in that particular type of e-commerce. The document concludes that e-commerce has become the lifeblood of modern business and commerce.