E-commerce refers to the buying and selling of goods and services over electronic systems like the Internet. It allows consumers to browse catalogs, place items in a shopping cart, pay for purchases, and receive order receipts online. There are several types of e-commerce including business-to-business (B2B), business-to-consumer (B2C), business-to-government (B2G), consumer-to-consumer (C2C), and mobile commerce (M-commerce). E-commerce provides advantages such as faster transactions, global reach, and lower costs, but also disadvantages like the inability to examine products personally and security risks.