Amazon has finally topped Walmart to become the largest company in the world by sales, but the latter is growing, ironically, with Amazon's forte -- e-commerce. Walmart was late to the digital party, but it's now up to speed, and it has a huge advantage over Amazon with its huge base of physical stores.

Walmart and Costco are among the largest retailers in the world. Walmart is boosting its profit margins with online ad growth and e-commerce sales. Costco has high comparable sales growth rates, suggesting customers are returning often and buying more products

Walmart is best known for its sales, but it recently made a noteworthy buy on Long Island: itself. The big-box retailer purchased its location at 965 Broadhollow Road in Farmingdale’s Republic Plaza for $48 million,