Walmart and Amazon are in the same market, which is an oligopoly. These firms, in addition to Target, make up a majority of the all sales in the market. There are many other smaller firms, but these firms combine to make up a relatively small part of the market and don't have the market power that Walmart, Amazon, and Target have. A major difference between the two firms, however, is that Walmart primarily conducts their sales in person, while Amazon does all of their sales online. Walmart, however, has been expanding their sales methods to include online sales. Another difference is the actual sellers. While Walmart purchases all of their inventory and sells that inventory, Amazon has taken more of a hybrid approach. A majority of the products sold by Amazon are from their own inventory. However, they also work with other companies and allow them to sell their products through Amazon.