E-commerce, or electronic commerce, refers to the buying and selling of goods and services through electronic mediums like the internet, which provides advantages such as global reach, reduced transaction costs, and the ability for 24/7 shopping. However, it also has disadvantages, including setup costs and potential issues with personal touch and delivery. There are four main types of e-commerce: B2C, B2B, C2C, and C2B, each characterized by the nature of the transaction between parties.