Facebook CEO Mark Zuckerberg said he didn't fully understand the divide between news and opinion sections at media outlets until he visited the headquarters of News Corp. and Fox in 2017.

The news-opinion divide is standard practice at most outlets, which prohibit collaboration between staff that report the news and staff that produce opinion content.

Facebook is one of the largest media companies on the planet.

Zuckerberg made the statement during a live-streamed conversation with News Corp. CEO Robert Thomson about Facebook's new "News Tab" feature, which began rolling out to users Friday.

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The divide between news and opinion sections is the golden rule at most media outlets, but many people don't know about or understand the distinction. As it turns out, the CEO of one of the world's largest media companies learned about it shortly after Donald Trump was elected.

Facebook CEO Mark Zuckerberg said Friday that he didn't fully understand the news-opinion divide until early 2017, when he toured the headquarters of Fox parent company News Corp. Zuckerberg made the comment during a live interview with News Corp. CEO Robert Thomson.

"Something you were saying that really stuck with me is internally at your organizations there's such a stark distinction between news and opinion," Zuckerberg said. "As a consumer of the stuff, sometimes the stuff blends together and even despite how rigorous your organization and others are at making sure those are kept separate … it's not always clear to the public."

Before seeing how News Corp. and Fox operated, Zuckerberg said, the distinction between news and opinion was often unclear to him "as someone who watches a lot of TV." Thomson interjected by joking, "I think you should read more newspapers."

It's true that news outlets have struggled to educate consumers about their own editorial standards — roughly a third of Americans have difficulty distinguishing between news and opinion content, according to a study by the American Press Institute.

"Most readers do not [understand the distinction]," Philadelphia Inquirer Editorial Page Editor Harold Jackson told CJR. "Most readers believe there is collusion between the editorial writers and the news writers and editors, that one reflects the other."

Zuckerberg seemingly brought up the news-opinion divide to make a broader point about how the general public doesn't understand rigorous policies maintained within organizations. Facebook has struggled with similar lack of public understanding, he said.

"The work around AI and algorithms is probably one of the least understood parts of what we do," Zuckerberg said. "I'll routinely see people say of course these sites are optimizing for content for whatever's going to make people spend the most time on these services. That's actually not true. … we actually optimize the systems for facilitating as many meaningful interactions as possible."

Zuckerberg was speaking with Thomson to publicize the rollout of Facebook's News Tab, a new feature launched Friday. Facebook is reportedly paying some publishers as much as $3 million a year to list news articles in the tab.

A Facebook spokesperson was not immediately available for comment.