Walmart is among the world's largest retailers, serving hundreds of millions of customers a week through thousands of stores and a rapidly growing online business. Groceries account for the bulk of US sales, giving the company steady traffic that supports higher-margin lines like advertising, marketplace fees and the Walmart+ membership. Sam's Club adds a warehouse-club format, and international operations span Mexico, Canada, India and beyond. Scale in purchasing and logistics lets Walmart compete relentlessly on price.