This document defines e-commerce and describes the different types. It begins by defining e-commerce as the buying and selling of goods and services over the internet. It then describes the three main types: B2B which is business to business and accounts for 80% of e-commerce, B2C which is direct sales from companies to consumers, and C2C which is consumer to consumer sales between individuals. The document lists advantages such as 24/7 access and easier branding. It also notes disadvantages like not everyone having internet access and inability to examine products physically. Finally, it states there are existing e-commerce sites in Bangladesh.