The Wild Wild West of the Internet is a great shopping adventure!
WebStores, Sites for business to advertize their services, products, locations. These provide access to the actual stores where the selling will occur.
eComerce, Sites for businesses who will complete transactions without human interference. The system them passes the duty to provide the purchased goods to another system that may include Human workers in some or many steps.
Rockauto, an online catalog with a shopping cart, checkout, payment, and product return for a hugh selection of parts for automotive devices and
Amazon, an online shopping and delivery system similar to Rockauto but providing a marketplace environment for various 'sellers' who actually provide products. In some cases Amazon will also warehouse products. In some areas they also provide product pickup at 'lockers' close to a delivery location.
In eComerce sites there may not be a storefront location that a customer will ever walk into to do business.