Uber spent $5.2 billion in 3 months. Here's where all that money went.

Uber also spent heavily on driver rewards connected to its IPO. The company spent $299 million in another one-time charge for those driver payments.

Khosrowshahi told CNBC Friday morning that these one-off charges, while painful, were well-deserved and important to retaining drivers and talent.

"The IPO for us was a once in a lifetime moment," he said. "And it was a really important moment for the company. Some of what we did, like the driver appreciation reward, almost $300 million that we put in the hands of over a million drivers globally, was really important for us to do. It created a messy P&L from an accounting standpoint that I think is hiding underlying trends that are actually very, very healthy for the company."

Research and development is the biggest expense line for Uber that's not a one-off related to the IPO.

Between its Advanced Technologies Group that's developing self-driving cars in Pittsburgh, Toronto, and San Francisco; New Mobility that's launching new e-bikes and adding public transit options to Uber's app; Elevate, the unit dedicated to making flying taxis a reality; and improvements to its core ride-hailing business's dispatching, routing, and fare algorithms, there's plenty to spend money on.

Read more: Uber has raised another $1 billion for its self-driving unit, which is now valued at more than $7 billion

Here's how Uber defines R&D spend in regulatory filings:

Research and development expenses consist primarily of compensation expenses for engineering, product development, and design employees, including stock-based compensation, expenses associated with ongoing improvements to, and maintenance of, our platform offerings, and ATG and Other Technology Programs development expenses, as well as allocated overhead. We expense substantially all research and development expenses as incurred.

General and administrative spend consists of everything like rent for office space around the world, legal counsel, human resources, and other expenses.

"We expect that sales and marketing expenses will increase on an absolute dollar basis and vary from period to period as a percentage of revenue for the foreseeable future as we plan to continue to invest in sales and marketing to grow the number of platform users and increase our brand awareness," the company has said in regulatory filings. "The trend and timing of our brand marketing expenses will depend in part on the timing of marketing campaigns."

Perhaps not surprisingly, Uber spends massive amounts of money on marketing. Even despite laying off 400 employees from its marketing department in July (a move that won't be counted in this earnings report, but will be reflected in the third quarter), the company says this number likely won't be going down.

Read more: Uber marketing employees describe this week's 'bloodbath' when the company laid off 400 employees in more than a dozen countries this week

"The reorganization is about improving effectiveness and it's about thinking about where we're going to be for the next five years of the company versus where we come from," Khosrowshahi said on the call. "My expectation is that our marketing spend, I can't speak to the — for the second half of the year, but our marketing spend for the next few years is actually going to both increase and be more effective as a result of the changes that we're making in the marketing organization."

In regulatory filings, Uber says its sales and marketing spend consists "primarily of compensation expenses, including stock-based compensation to sales and marketing employees, advertising expenses, expenses related to consumer acquisition and retention, including consumer discounts, promotions, refunds, and credits, Driver referrals, and allocated overhead. We expense advertising and other promotional expenditures as incurred."

This line includes many of the driver-focused employees in operations support centers, like Green Light Hubs, throughout the world. This amount, though small, is likely to decrease going forward, Uber has said, as it becomes more efficient in "supporting platform users."

As time goes by, certain assets may lose value. For physical things, like buildings, vehicles, or machinery, this reduction is known as depreciation. For intangible assets, this is called amortization, and is slightly more concrete to calculate.

Unlike tangible items, assets that amortize do so on a "straight-line" basis, according to Investopedia, meaning the same amount decreases from an item's value every period until it reaches zero. Examples of assets that might amortize include costs from capital raises, patents and trademarks, or other intellectual property.