E-commerce refers to the buying and selling of goods and services online. Some key advantages of e-commerce include not requiring a physical store, offering many product choices, and providing access to remotely located stores. However, e-commerce also has disadvantages such as the inability to see products before purchase and requiring internet access. Common e-commerce types are business-to-business, business-to-consumer, consumer-to-consumer, and government-to-citizen transactions. Social media is also an important marketing tool for e-commerce as it allows easy product promotion through platforms like Facebook and Twitter.