On Tuesday, Best Buy (BBY 3.22%) announced a dramatic expansion of its online store, and investors rewarded the company by bidding its stock price up. Shares of the sturdy electronics retailer closed the trading session more than 3% higher, on a day when the S&P 500 index slumped by 0.6%.

A better outlet for Best Buy

Well before market open Tuesday morning, Best Buy announced that its new Best Buy Marketplace, an expansion of its existing e-commerce channels, was open for business. It added that through Marketplace's web portal and mobile app, customers now have access to more than double the number of products.

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Among these fresh offerings are new brands and types of products that haven't previously been offered electronically by Best Buy. Customers will be able to purchase goods from third-party sellers via the website and app. This will allow them to buy products that fall outside the electronics retail space.

The company added that the rollout of Marketplace is its largest-ever expansion of a sales outlet.

In its press release trumpeting the launch, Best Buy Chief Marketplace and eCommerce Officer Frank Bedo said this allows the company to offer "not only more of the latest technology, but a massive new collection of products outside of the tech space so we can truly offer the full experience [customers] need."

A justifiable reaction from the market

It nearly goes without saying that the more goods and/or services a retailer can offer, directly or otherwise, the more they stand to earn in revenue. Best Buy didn't go into detail about how it would split the take with those third-party sellers, but given the retailer's size and prominence, it's likely getting a decent cut. Investors were right to be optimistic about the company's latest news.