This document discusses different types of e-commerce models. It describes business-to-business (B2B) e-commerce as the sale of goods or services between businesses via an online portal to improve sales efficiency. Examples given are automobile manufacturers purchasing parts from other companies. Business-to-consumer (B2C) e-commerce refers to businesses selling products and services directly to consumers online or in-stores with no middleman. Examples of B2C include online retailers and brick-and-mortar stores like Walmart, Target, and clothing brands. The document provides definitions and examples of various e-commerce models including B2B, B2C, B2E, B2G, C2B