Amazon and Walmart are the two top retailers in America, perhaps the world. Amazon does it on-line, Walmart does it the old fashioned way, although Walmart is working the on-line angle as well.
Amazon is great, and they have the world's largest selection, even larger than Walmart. They have an advantage over Walmart because they don't have the overhead of a physical store. When shopping at Walmart, you can use your smart phone to price compare with Amazon. But Amazon isn't always cheaper. An example I like is canning jars. The same product at
Amazon and
Walmart, costs $32.92 at Amazon, and $29.49 at Walmart. At amazon shipping is free for prime members. What you're paying for is to have UPS bring it to your door. At Walmart, an employee moves a pallet of jars with a fork-lift, and you have to pick it up and get it "home". I've found that large, heavy items are often cheaper at Walmart, whereas smaller, easy-to-ship items are cheaper at Amazon. At Walmart you can see and handle the item, at Amazon you have to use your imagination. Keep in mind the sales tax advantage for states where Amazon doesn't yet charge sales tax.
Both companies are great. They fill different niches. You'd never buy ice from Amazon, or fresh food, but for many things it's easier to buy from Amazon and not have to travel to the store.