E-commerce, or electronic commerce, refers to the buying and selling of goods and services over the internet. It includes various business models such as Business-to-Consumer (B2C), Business-to-Business (B2B), and Consumer-to-Consumer (C2C) platforms. Popular e-commerce sites like Amazon, Alibaba, and eBay allow consumers to shop online with convenience and a wide range of choices. Key components include online payment systems, digital marketing, and logistics for order fulfillment. The e-commerce industry has seen significant growth due to advancements in technology, increased internet penetration, and changing consumer behaviors. It has transformed traditional retail, enabling businesses to reach global audiences, and offers personalized shopping experiences through data analytics and AI. Challenges include cybersecurity, competition, and ensuring a seamless user experience.