• Amazon reported weaker-than-expected revenue for the second quarter and issued a disappointing forecast for the current period.
• Amazon's cloud business exceeded analyst estimates, but it's advertising unit came up short.
• The stock is up 21% year to date as of Thursday's close.

Amazon reported weaker-than-expected revenue for the second quarter on Thursday and issued a disappointing forecast for the current period. The shares slid as much as 6% in extended trading.

Here's how the company did:

• Earnings: $1.26 per share vs. $1.03 per share expected by LSEG
• Revenue: $147.98 billion vs. $148.56 billion expected by LSEG

Wall Street is also looking at these key numbers:

• Amazon Web Services: $26.3 billion vs. $26 billion in revenue, according to StreetAccount
• Advertising: $12.8 billion vs. $13 billion in revenue, according to StreetAccount

Amazon forecast revenue in the current quarter to be between $154 billion and $158.5 billion, representing growth of 8% to 11% year over year. The mid-point of that range, $156.25 billion, trailed the average analyst estimate of $158.24 billion, according to LSEG.

Amazon continues to reckon with sluggish growth in its core retail business, as competition heats up, largely from discount sites like Temu and Shein, which allow Chinese merchants to sell cheap items to U.S. consumers.

Sales in its online stores segment grew just 5% year over year. Revenue from third-party seller services, which includes commissions, and fulfillment and shipping fees, accelerated faster, expanding 12% during the quarter.

"We did come in a little short on revenue growth in North America versus our internal estimates," finance chief Brian Olsavsky told reporters on a call after the report.

Olsavsky said the revenue miss was driven by consumers choosing to buy cheaper products, leading to lower average selling price (ASP).

"What we're seeing is really around ASP and lower ASP in products selected by customers," Olsavsky said. "They are continuing to be cautious in their spending and trading down to lower ASP products."

At an event with Chinese sellers in June, Amazon said it plans to launch a discount store that will feature mostly unbranded items priced below $20, according to a presentation viewed by CNBC. The store is expected to offer apparel, home goods and other products.

Amazon expects third-quarter operating income to be in the range of $11.5 billion to $15 billion, compared with $11.2 billion in the year-ago period. Analysts surveyed by StreetAccount forecast $15.3 billion in operating income.

In cloud, AWS beat estimates, growing 19% from a year earlier, but the unit is expanding at a slower rate than rivals Microsoft and Google. Both of those companies reported cloud growth of 29% in their respective earnings reports, though their numbers include more than just cloud infrastructure.

Amazon's advertising revenue jumped 20% to $12.77 billion during the quarter, falling just shy of estimates. The unit has emerged as one of the biggest profit generators, and although most ad sales continue to come from sponsored product listings on its online store, the company has added newer offerings and grown its market share in the digital ad segment, where it competes with Meta and Alphabet.

Among online ad companies, Meta had the strongest quarter, reporting revenue growth of 22%. Google's ad business grew just 11% in the quarter. Snap said on Thursday that revenue increased 16% from a year earlier.

Net income at Amazon doubled from a year earlier to $13.5 billion, or $1.26 a share, from $6.75 billion, or 65 cents a share, reflecting mass cost-cutting efforts across the company.

Olsavsky said the company is attributing part of the weakness in its guidance to consumers being distracted by world events, which he said made it "a tough quarter to forecast." He highlighted the Olympics, which began last month in Paris, and the attempted assassination of Donald Trump at a rally in July.

"No matter what you're selling or providing to a customer base, customers only have so much attention and the things like the Olympics, although they don't happen that often, we do see different traffic patterns around those events," Olsavsky said. "When high-profile things happen or the assassination attempt a couple of weeks ago, you see that people shift their attention around news."

Disclosure: CNBC parent NBCUniversal owns NBC Sports and NBC Olympics. NBC Olympics is the U.S. broadcast rights holder to all Summer and Winter Games through 2032.

This story is developing. Check back for updates.

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