E-commerce refers to the purchasing and selling of goods and services over electronic networks. There are four main types of e-commerce: business-to-business, business-to-consumer, consumer-to-business, and consumer-to-consumer. E-commerce provides advantages like increased sales, decreased costs, and access to global markets, but also faces disadvantages such as not all people having internet access or trust in online financial transactions. Overall, e-commerce is still developing to improve security and efficiency as applications have existed since the 1970s.