E-commerce refers to business transactions conducted over computer networks and includes four main models: business-to-business (B2B) transactions that allow companies to collaborate and trade goods; business-to-consumers (B2C) transactions where businesses offer and consumers purchase services online; business-to-government (B2G) transactions for paying taxes and applying for licenses; and business-to-employees (B2E) transactions for payroll, welfare schemes, and obtaining employee feedback.