(First of two parts. Next week: How to evaluate what’s real news and what’s not.)

An old newspaper saying goes like this: "If your mother says she loves you, check it out." Professors and editors tell it to future journalists and young journalists as a reminder to confirm facts, even ones that seem 100 percent true. In this digital era, a similar saying has an important message for all of us: "Don't believe everything you read online." That's also not new, but gained urgency during last year's presidential race as untrue claims masquerading as news were heavily shared and retweeted. Bogus "news" posts from partisan sites show up prominently in Google search results, which makes them seem valid. Unlike journalism, USA Today columnist Michael Wolff notes, "social media has no standards or rules. Anybody can make this stuff up. In fact, the more outrageous it is the more page views it gets."

The troubling phenomenon is called fake news, which refers to made-up or exaggerated claims presented at blogs or media-like sites that look credible. (This doesn’t refer to real news about opinions on topics such as climate change, a candidate or Russian hackers. It also doesn't refer to satire from The Onion or "The Daily Show.") When spread on social media, hoaxes may be taken as fact by people who trust friends' posts and share their political views. Here are three stories that circulated last fall, though each was totally false: (1) Pope Francis endorsed Donald Trump. (2) Hillary Clinton ran a ring holding kidnapped kids under a pizza shop in Washington, D.C. (3) Thousands of Trump rally participants in Manhattan chanted "We hate Muslims, we hate blacks, we want our great country back."

President Obama in November urged news consumers to pick information sources carefully and avoid "this dust cloud of nonsense," as he called it at a rally for Clinton, the Democratic presidential nominee. "People, if they just repeat attacks enough, and outright lies over and over again, as long as it's on Facebook and people can see it, as long as it's on social media, people start believing it," he said. (See video below.) Indeed, a study by the Pew Research Center shows that 44 percent of Americans get their news from Facebook. That platform and Twitter fill a void created by shrinkage in the number, size and popularity of newspapers.

After at first trying to minimize its role and responsibility, Facebook in mid-December took steps to limit misinformation. It’s easier now for the 1.8 billion users to report fake news. New partnerships with outside groups help Facebook spot false articles. The company also tightened advertising rules to keep fake news originators – sometimes located overseas -- from profiting. "We've focused our efforts on the worst of the worst, on the clear hoaxes spread by spammers for their own gain," a recent post by Facebook says.

Writer says: "I was horrified to hear my own relatives at a family party last summer repeating the lie that Baltimore protesters against police violence had chanted 'kill a cop.' . . . 'It's true — I saw it on Facebook,' one replied." -- Maria Bustillos of Los Angeles, writing at Nieman Lab (Harvard University journalism site)

Facebook says: "It's important to us that the stories you see on Facebook are authentic and meaningful. . . . We're going to keep working on this problem for as long as it takes to get it right." -- Adam Mosseri, vice president

Editorial says: "A big part of the responsibility for this scourge rests with internet companies like Facebook and Google, which have made it possible for fake news to be shared nearly instantly with millions of users and have been slow to block it." – The New York Times