A very brief overview into a couple models for ecommerce.
B2B - Business to business. Transactions between companies, common for specialised industries such as engineering, but also common for more general use, such as marketing services. B2C - Business to customer. The most standard to use as a customer. Clothing stores, food, products, etc. A retailer or distributor may sit in the middle, e.g. you buy from a place like Officeworks, rather than Logitech. C2C - Customer to customer. Often referred to as 'marketplaces', such as eBay or Gumtree. D2C - Direct to customer. Where the business sends directly to the customer. You can buy Logitech products from Officeworks, but you can also buy direct.