Q: What happened and why is it a big deal?

A: The Guardian newspaper published a highly classified April U.S. court order that allows the government access to all of Verizon's phone records on a daily basis, for both domestic and international calls. That doesn't mean the government is listening in, and the National Security Agency did not receive the names and addresses of customers. But it did receive all phone numbers with outgoing or incoming calls, as well as the unique electronic numbers that identify cellphones. That means the government knows which phones are being used, even if customers change their numbers.

This is the first tangible evidence of the scope of a domestic surveillance program that has existed for years but has been discussed only in generalities. It proves that, in the name of national security, the government sweeps up the call records of Americans who have no known ties to terrorists or criminals.

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Q: Why does the government even want my phone records?

A: They're not interested in your records, in all likelihood, but your calls make up the background noise of the global phone system.

Look at your monthly phone bill, and you'll see patterns: calls home as you leave work, food delivery orders on Friday nights, that once-a-week call to mom and dad.

It's like that, except on a monumentally bigger scale.

The classified court ruling doesn't say what the NSA intends to do with your records. But armed with the nation's phone logs, the agency's computers have the ability to identify what normal call behavior looks like. And, with powerful computers, it would be possible to compare the entire database against computer models the government believes show what terrorist calling patterns look like.

Further analysis could identify what are known in intelligence circles as "communities of interest"—the networks of people who are in contact with targets or suspicious phone numbers.

Over time, the records also become a valuable archive. When officials discover a new phone number linked to a suspected terrorist, they can consult the records to see who called that number in the preceding months or years.

Once the government has narrowed its focus on phone numbers it believes are tied to terrorism or foreign governments, it can go back to the court with a wiretap request. That allows the government to monitor the calls in real time, record them and store them indefinitely.

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Q: Can the government read emails?

A: Not under this court order, but it's not clear whether the NSA is monitoring email content as part of this program.

In 2006, former AT&T technician Mark Klein described in federal court papers how a "splitter" device in San Francisco siphoned millions of Americans' Internet traffic to the NSA. That probably included data sent to or from AT&T Internet subscribers, such as emails and the websites they visited.

Most email messages are sent through the Internet in "plain-text" form, meaning they aren't encrypted and anyone with the right tools can view their contents. Similar to an old-fashioned envelope and letter, every email contains details about whom it's from and where it's supposed to go.

Unlike postal letters, those details can include information that can be linked to a subscriber's billing account, even if he or she wants to remain anonymous.

In May 2012, Wyden and Udall asked the NSA how many people inside the United States had their communications "collected or reviewed."

The intelligence community's inspector general, I. Charles McCullough III, told the senators that providing such an estimate "would likely impede the NSA's mission" and "violate the privacy of U.S. persons."