This document provides an overview of e-commerce. It defines e-commerce as the process of buying and selling goods and services online. The main categories of e-commerce are business-to-business, business-to-consumer, consumer-to-consumer, government-to-business, and mobile commerce. A brief history of e-commerce is given starting from the 1970s. Advantages and disadvantages of e-commerce for both customers and businesses are outlined. The document concludes that e-commerce has led to more competition, marketplaces and transactions through use of the internet.