Apple has invested $1 billion into Didi Chuxing, a major Chinese ride-hailing service. Among other things, the move is intended to help Apple better understand China, its second-largest market after the US.

"We are making the investment for a number of strategic reasons, including a chance to learn more about certain segments of the China market," Apple CEO Tim Cook tells Reuters. "Of course, we believe it will deliver a strong return for our invested capital over time as well." Cook also sees potential avenues for collaboration between the two companies.

"Didi exemplifies the innovation taking place in the iOS developer community in China," Cook says in a statement. "We are extremely impressed by the business they've built and their excellent leadership team, and we look forward to supporting them as they grow." Didi CEO Cheng Wei calls the investment "enormous encouragement and inspiration for our four-year-old company."

The investment is the largest that Didi has ever received. Didi Chuxing, formerly known as Didi Kuaidi, is by far the biggest service of its type in China, holding over 87 percent of the market for private car-hailing and presenting a significant challenge for rivals such as Uber. (Lyft, meanwhile, has chosen to partner with Didi.) The service has over 300 million users across more than 400 Chinese cities, and says it completes over 11 million rides a day.

Apple's own interest in the field of transportation has been limited so far, but the company is widely rumored to be building a car of its own. Currently, it develops the CarPlay infotainment system that links to drivers' iPhones. "That is what we do today in the car business, so we will have to see what the future holds," says Cook.