Every company has a chart that defines it.

The chart for Apple (NASDAQ:AAPL), for instance, would show iPhone sales -- their trend or the evolving share of revenue they account for. After all, the iPhone has made Apple the most valuable company in the world.

That's what a defining chart is. It reflects the core or unique quality that's most responsible for a company's success.

Few are more striking than Wal-Mart's (NYSE:WMT) defining chart. It compares the annual revenue of Wal-Mart to other large companies -- say, those on the S&P 500, which tracks the leading companies in the United States.

A bar chart showing the five companies with the highest revenues on the S&P 500

Data source: YCharts.com. Chart by author.

Despite the enormous size of these other companies, most of which have higher market caps than Wal-Mart, their annual revenues pale in comparison to the Arkansas-based retailer's.

Wal-Mart's revenue over the last 12 months adds up to $486 billion. That's more than twice Apple's total revenue -- which, not to belabor the point, is the most valuable company in America.

It's this stark contrast between sales and value that reflects Wal-Mart's core business model: Selling lots of stuff at everyday low prices.

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This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.