Here's what 'unmasking' — the phrase everyone keeps using about former national security adviser Michael Flynn — means

• Former national security adviser Michael Flynn made headlines this month following several bombshell developments in the Justice Department's case against him and his role in the FBI's Russia investigation.
• This week, acting director of national intelligence Richard Grenell declassified the names of government officials who were involved in "unmasking" Flynn's name in intelligence reports monitoring the communications of Sergey Kislyak, then Russia's ambassador to the US.
• "Unmasking" is a term the intelligence community uses which refers to revealing the identity of someone on a monitored communication.
• "Unmasking" is legal and typically occurs when intelligence officials need more context about the surveillance on a foreign actor to make sense of the information they've received.
• In Flynn's case, the National Security Agency was monitoring Kislyak's communications and discovered he was discussing Russian sanctions with a US person whose identity was masked.
• Flynn's identity was later unmasked as US officials determined if they needed to investigate whether he violated federal law.
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The controversy surrounding former national security adviser Michael Flynn made headlines again this month following several bombshell developments related to the Justice Department's case against him and his role in the FBI's investigation into Russian interference in the 2016 US election.

Last week, the department abruptly moved to drop its case against him, sending shockwaves through the country and raising fresh concerns that President Donald Trump's Justice Department, led by Attorney General William Barr, was putting politics above the rule of law.

This week, Richard Grenell, the acting director of national intelligence, also declassified the names of government officials who were involved in "unmasking" Flynn's name in intelligence reports from 2016 surveilling the communications of Sergey Kislyak, then Russia's ambassador to the US.

"Unmasking" is a term the intelligence community uses which refers to revealing the identity of someone on a monitored communication.

The intelligence community frequently monitors the correspondence of foreign actors — such as businessmen, or ambassadors — operating on US soil. If the monitored foreign actor is speaking with a US citizen, the US citizen's name will be "masked" on the report or transcript to protect his or her identity.

The report or transcript would list the "masked" person with some kind of generic descriptor like "Person 1." In this way, Person 1's correspondence would have been "incidentally collected," meaning he or she wasn't targeted but some of their communications were collected because the person that he or she was speaking to was targeted. "Incidental collection" is reportedly how Trump officials' communications were collected during the transition.

The foreign actor being monitored does not need to be the subject of an investigation to be surveilled, nor does Person 1. However, if a member of the intelligence community decides they need more information on the intelligence reports he or she is receiving about the foreign actor, that person can request an "unmask" of Person 1.

This does not mean Person 1 has committed a crime or is the target of an investigation, although Person 1 could also be unmasked if it was discovered that he or she had committed a crime.

"Unmasking" occurs when intelligence officials need more context about the surveillance on a foreign actor to make sense of the information they've received.

In Flynn's case, the National Security Agency was surveilling Russian ambassador Sergey Kislyak.

When they overheard him speaking to a "masked" individual about lifting Russian sanctions, US intelligence officials (it is unknown who requested his unmasking or who leaked his name) would have likely wanted to know if Kislyak was speaking to a friend who had no connection to the topic, or if he was speaking to someone like Flynn, with a political position.

The intelligence officials therefore needed Flynn's name "unmasked" to decide whether they should investigate that correspondence.

Unmasking itself is not illegal. However, leaking an unmasked name to the media or the public is illegal.

Grenell's move to declassify the names of officials involved in Flynn's unmasking comes after years of pressure from Republican lawmakers to reveal their identities.