Apple (NASDAQ:AAPL) CEO Tim Cook, fresh off reporting the most profitable quarter in corporate history, spoke at the Goldman Sachs Technology and Internet Conference earlier this week. During the talk, Cook spoke about some of the things Apple has been working on, along with what makes him optimistic about the company's continued success.

Here are three key quotes from his sit-down with Goldman COO Gary Cohn.

The opportunity in China is still enormous

"[China] has enormous opportunity. There's such an amazing number of people that are moving into the middle class. It's something like I've never seen in my lifetime before. And so we just ... opened four new stores in the last few weeks. And these four stores are in cities that have about, give or take, 9 million people [in] the city. ... And you think about 9 million people -- this is the size of New York City!"

Apple's store in Beijing. Source: Apple.

Cook noted that over the last five years, Apple sales in China have gone from less than $1 billion to $38 billion. The company has 19 stores in the country, with plans to double that by mid-2016. It has partnerships with all three major Chinese telecoms, as well as Internet services including Baidu, Tencent, and Youku Tudou.

But despite the phenomenal growth in China, Cook believes the company is still "not too far from the surface." There is potential for China to become an even larger market. The iPhone 6 and iPhone 6 Plus will help as Apple fends off local phone manufacturers such as Xiaomi and Huawei.

Additionally, Cook told Cohn that there are other opportunities just like China where Apple hasn't spent as much energy. India, for example, represents another major opportunity with similar characteristics to China.

The App Store for Apple Watch

"The third-party apps -- the things third parties are working on -- I'm super excited about. And so I think it's going to be, everybody's going to have their favorite thing. Just like when the App Store came out. ... And the way you felt with your favorite apps, and so you're going to have a feeling like that."

The Apple Watch comes in several styles, but the apps will make you want to buy it. Source: Apple.

While there are already several smartwatches on the market, the key factor for the Apple Watch is the App Store. Just as the App Store is a big differentiating factor for the iPhone and iPad, Cook believes it is what will make the Apple Watch a success.

Apple released WatchKit to developers last fall and is giving them about six months to tinker around before the actual device ships. Obviously, it's difficult to program for a device you've only seen and maybe interacted with for a couple minutes. Once the device is out in the wild, the App Store could take off by providing dozens of uses for the Apple Watch that the competitors don't offer.

The partnership with IBM is about to take off

The truth is, enterprise has not moved to mobility in a big way like the consumer has. There's still so many people stuck at their desks in the enterprise. It's unbelievable when you really think about it.

Apple's iPad could still grow in the enterprise market. Source: Apple

Apps, and the ability to easily program new apps with Apple's new programming language Swift, have been a key driver for Apple's partnership with IBM. The ability to create customized productivity apps for different professions -- from pilots to nurses -- will set Apple apart from the competition as more enterprises shift to mobile devices.

Cook sees the strengths of IBM and Apple as very complementary: IBM has deep knowledge of numerous verticals and a huge amount of field resources, and Apple has the devices and platform that enterprises want to use. And with the penetration of mobile devices in the enterprise space still relatively low, there's a lot of room to grow in the space. That's where IBM can help.

The "laws of large numbers"
At the start of the talk, Cook said Apple doesn't believe in "the laws of large numbers," meaning that growth slows as the company gets bigger. That is not really the law of large numbers, but that's beside the point.

Apple is focused on delivering the best experience to its customers, and there's no reason to think it will change course in 2015. If the first-quarter results are any indication, the "laws of large numbers" don't apply to Apple.