Final answer:
C2C (consumer-to-consumer) e-commerce is the type of e-commerce when one consumer sells directly to another, as seen in online auctions like eBay.
Step-by-step explanation:
The type of e-commerce that occurs when one consumer sells directly to another, such as in an online auction, is known as C2C e-commerce. C2C stands for customer-to-customer or consumer-to-consumer, where individuals sell products or services to other consumers over the internet. This type of e-commerce has become increasingly popular with the advent of online platforms that facilitate these transactions, enabling consumers to reach a wider market. An example of C2C e-commerce would be an online marketplace where used goods are sold by one consumer to another, such as eBay or Craigslist.