If I don't understand a company's products or services, I won't buy the shares. It's as simple as that. Why? Knowledge of what a company sells helps us paint a more accurate picture of that company's revenue prospects.

We all have our own specialties and favorite industries, but here are three stocks just about anyone can understand.

Two grocery bags stuffed with leafy vegetables sit on someone's front porch

Image source: Getty Images.

Walmart

Who hasn't set foot in a Walmart (NYSE:WMT) store? Although Walmart sells medicine, clothing, toys, and many other items, grocery is its mainstay, making up 56% of revenue at its U.S. stores.  

Walmart also benefits from the shift in shopping from in-store to online. U.S. grocery is the fastest-growing e-commerce product category and will reach $38 billion by 2023 from almost $20 billion last year, according to eMarketer. Walmart said its U.S. e-commerce sales grew 37% in fiscal 2020 (which ended Jan. 31). With the coronavirus outbreak keeping consumers at home but still shopping for essentials, it's likely Walmart will see continued e-commerce growth in the current quarter.

Last month, the company announced the creation of 150,000 new jobs, so it's clear that demand at Walmart is on the rise. The shares have surpassed Wall Street's average price target, gaining 9% this year. However, considering Walmart's focus on e-commerce and strength in grocery, I expect further upside in the long term.

Procter & Gamble

Under normal circumstances, there is always a need for products made by consumer staples giant Procter & Gamble (NYSE:PG). Most of us recognize names like Charmin toilet paper, Tide laundry detergent, and Pampers diapers. Well, those were some of the products that boosted Procter & Gamble's revenue over the past several weeks. In the quarter that ended March 31, the company posted a 5% increase in net sales to $17.2 billion, led by two product categories: fabric and home care, and baby and family care. The fabric and home care business -- which made up the biggest share of 2019 revenue at 33% -- saw an 8% increase in net sales.

Procter & Gamble reported strong demand in North America and some European markets due to the coronavirus outbreak as people stocked up. In certain Asian markets, though, demand faltered as quarantined consumers were unable to shop.

We won't see this sort of picture every quarter. But Procter & Gamble's products are market leaders -- for example, Tide is the best-selling laundry detergent in the U.S. -- so we can expect more revenue growth from here. Procter & Gamble also can be counted on for payouts to investors, most recently increasing the quarterly dividend by 6% to $0.7907. That represents the 64th consecutive year of increases.

Procter & Gamble's stock has rebounded from its earlier declines, and now is just below where it started the year. In spite of the rebound, it remains interesting for the long-term investor. The company has made it through a quarter that was difficult for most, and it will continue to benefit from sales of market-leading products.

Nike

Nike (NYSE:NKE) sells items most of us know well: sneakers, t-shirts, and other sportswear. Though many companies make this sort of gear, Nike has brand recognition -- and a strategy -- that is helping it weather the current coronavirus crisis.

While Nike had to temporarily close 75% of its stores in Greater China, the company still managed to increase digital sales there by more than 30% in fiscal 2020's third quarter (which ended Feb. 29). This digital strategy should also help the company manage the crisis in Europe and North America.

On the recent earnings call, Nike said it was making its Nike Training Club Premium, an app offering workouts and tips, free to all U.S. Nike members for 90 days. Similar moves in China resulted in more signups for Nike activity apps, and Nike said that directly translated into the gains in digital sales in the quarter.

Nike's earnings this year may not look as good as last year's due to the temporary store closures and cancellation of global athletic events due to the coronavirus pandemic. Professional sporting events represent advertising opportunities for the brand. But we can count on Nike to bounce back once the crisis is over, as it remains connected digitally with fans through its apps now.

Brand power will also keep Nike winning. The Jordan brand posted its first billion-dollar quarter in the second quarter -- 17 years after basketball legend Michael Jordan retired. Nike's stock has declined 16% this year, but it still isn't exactly cheap at 32 times earnings. That's higher than rival Adidas, which trades at just under 23 times earnings.

Still, Nike is a consumer discretionary company that's well positioned for long-term growth once this difficult time has passed.