Q: What happened?

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.

Q: How is this different from the wiretapping that was going on under President George W. Bush?

A: In 2005, the New York Times revealed that Bush had signed a secret order allowing the NSA to eavesdrop on Americans without court approval, a seismic shift in policy for an agency that had previously been prohibited from spying domestically. The scope of that program has never been known, but it allowed the NSA to monitor phone calls and e-mails. While wiretapping got all the attention, the government was also collecting call logs from American phone companies as part of that program, a U.S. official said Thursday. After the wiretapping controversy, the collection of call records continued, albeit with court approval. That's what we're seeing in the newly released court document: a judge's authorization for something that began years ago with no court oversight.

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

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

Q: Why just Verizon?

A: It's probably not. A former U.S. intelligence official familiar with the NSA program says that records from all U.S. phone companies would be seized. Only the court order involving Verizon has been made public.

Q: Does that mean someone had to show probable cause that a crime was being committed?

A: The seizure was authorized by the Foreign Intelligence Surveillance Court, which operates under different rules from a typical court. Probable cause is not required. The court was created by the Foreign Intelligence Surveillance Act of 1978 and is known in intelligence circles as the FISA court. Judges appointed by the president hear secret evidence and authorize wiretapping, search warrants and other clandestine efforts to monitor suspected or known spies and terrorists. For decades, the court was located in a secure area at Justice Department headquarters. That changed in 2008 with the construction of a new FISA court inside the U.S. District Court in Washington. The courtroom is essentially a vault, designed to prevent anyone from eavesdropping.

Associated Press