E-commerce refers to the buying and selling of goods and services online. The document provides a brief history of e-commerce beginning in 1979 and highlights some key events and companies in the development of e-commerce through the 1990s and 2000s. It then discusses different models of e-commerce including business-to-consumer, business-to-business, and consumer-to-consumer. Finally, it covers important aspects of running an e-commerce business like payment systems, logistics, legal issues, and customer types.