Republicans are salivating and Democrats are anxious over the prospects of an election-year indictment for Hillary Clinton over her emails.

The clamor around Clinton's potential legal woes hit a peak this week, when news broke that Bryan Pagliano, a former State Department aide who set up the server in Clinton's home in New York, was granted immunity to speak freely with the FBI.

The report sparked a flurry of new questions as to how serious the situation over the emails is for Clinton — who appears on course to become the Democratic presidential nominee.

But after nearly a year of a steady drip of incremental leaks surrounding the emails and ensuing investigation, some may be confused where things stand and what's at stake.

So here's are six things you need to know about the Clinton email investigation.

What are they actually investigating?

By now, it's public knowledge that Clinton used a personal email account housed on a private server located in her personal residence, instead of a government-issued email address, to conduct business when she served as President Barack Obama's Secretary of State.

Clinton apologized for using the server, which she has called a "mistake."

But it's not just the use of the server that could get Clinton in legal trouble.

Instead, there is an investigation that hinges around whether Clinton "knowingly" sent or received classified information on that server that put secrets at risk.

Clinton and her team say the classified information on the server was classified retroactively. That would mean the information was not classified at the time she sent or received it, but rather it was deemed classified as officials reviewed the emails on the server as they prepared to release them to the public.

The timing of that classification is key, experts say. And Clinton and her team insist she never sent or received information from her personal email address that was classified at the time she sent or received it.

"She’s very confident that there is no wrongdoing," Clinton spokeswoman Karen Finney said on MSNBC Friday afternoon.

Who is investigating?

There are multiple investigations about Clinton's use of a personal email server, including by the House Select Committee on Benghazi — which uncovered Clinton's use of the personal email account in the first place.

But the most consequential investigation is that being conducted by the FBI, which is seeking to determine whether there was any criminal wrongdoing by Clinton or her team in the handling of classified information.

What have we learned from the investigation so far?

So far, the investigation has shown that Clinton did send information that was deemed classified — but the timing of when it was classified is under review.

The investigation also showed there were phishing emails on her server reportedly sent from Russia.

But the New York Times reported Thursday that security logs Pagliano handed over to the FBI showed no evidence the server had been hacked by a foreign government or entity.

Clinton spokesman says campaign is "pleased" that Bryan Pagliano is cooperating with Department of Justice investigation into email server — Monica Alba (@AlbaMonica) March 3, 2016

It's also possible Clinton herself and some of her top aides could be interviewed, a development that would be sure to spark speculation about where the investigation is headed.

Clinton has said she will fully cooperate if she is asked to speak with investigators.

Who decides whether to bring charges?

While the FBI is conducting an investigation into whether Clinton criminally mishandled classified information, it is ultimately not up to the FBI to file charges.

That duty falls to the Department of Justice, led by Attorney General Loretta Lynch, an Obama political appointee.

Lynch would have final say in recommending federal prosectors convene a grand jury to seek an indictment.

If the FBI did recommend criminal charges be filed, it would put the Lynch and her agency in a bind.

Either she would have to sign off on seeking an indictment of the likely nominee of her political party. Or, face allegations of political favoritism.

Rep. Adam Schiff, a California Democrat and Clinton supporter, said Friday in an interview on MSNBC that the DoJ will likely be criticized for its response, no matter the outcome.

But experts say they are dubious of an indictment.

"I think any indictment is a long shot wholly unrelated to the timing — and for no other reason than the difficulty of shoehorning Secretary Clinton's actions, however troubling, into the criminal statutes that deal with the mishandling of classified information," said Stephen Vladeck, a law professor at American University's Washington College of Law.

"At least based on what we know so far, this case would've been a long shot in any year against any defendant, and so the fact that it's an election year and the putative defendant is the front-runner for the Democratic nomination is just icing on an already-frosted cake," Vladeck added.

Have other secretaries of state used personal email?

Yes, Colin Powell — who served as secretary of state under President George W. Bush — used personal email to conduct some business during his tenure.

In fact, he was found to have classified information in his personal email as well — which was discovered during a State Department investigation into Clinton's emails.

Powell, too, says the information was classified retroactively, and released an angry statement disputing the timing of the classification.

"If the Department wishes to say a dozen years later they should have been classified that is an opinion of the Department that I do not share," Powell said in the statement, published by ABC News.

Clinton has pointed to Powell's statement to say the State Department is going too far in determining the classification of information.

Is there past precedent for this type of investigation?

Yes, and experts say that past precedent is what could save Clinton from legal trouble.

A 2012 mishandling of classified information case against then-Director of the Central Intelligence Agency David Petraeus is widely seen as more severe than Clinton's alleged wrongdoing.

Petraeus admitted to knowingly providing "highly classified" information to his biographer and mistress Paula Broadwell. During the investigation into the mishandling of information, Petraeus also lied to FBI agents.

Petraeus plead guilty to only one misdemeanor charge for his actions, agreeing to pay a $100,000 fine and serve two years of probation.

And because Petraeus received what amounted to a slap on the wrist for his actions, some say it would be tough to punish Clinton more for her actions if it's proven that information she sent was not classified at the time she sent it.

"The key element that distinguishes Secretary Clinton’s email retention practices from Petraeus’ sharing of classified information is that Petraeus knowingly engaged in unlawful conduct, and that was the basis of his criminal liability," Anne M. Tompkins, the former U.S. attorney who prosecuted the Petraeus case, wrote in a USA Today op-ed last summer.

When will this all end?

The FBI's investigation could wrap by May, according to the New York Times.

At that time, we could learn whether the FBI recommended that criminal charges be filed, and if so, against whom.

Running for president under the shadow of a criminal indictment could be catastrophic for Clinton's chances.

But even if the FBI finds no wrongdoing, the issue is not likely to go away in the election.

Republicans, including GOP presidential front-runner Donald Trump, have been mentioning the email scandal repeatedly on the trail to question Clinton's judgement. They say the issue disqualifies her from being president.

At #CPAC, Ted Cruz alluding to the idea of Hillary Clinton going to jail over her email server: "Orange is the new Democratic blue." — Frank Thorp V (@frankthorpNBC) March 4, 2016

That line of attack is not expected to end, even if she is cleared of criminal wrongdoing.

The attacks have already taken a toll on Clinton's trustworthiness, according to polling on the race. Among Democratic primary voters ahead of Super Tuesday, Sen. Bernie Sanders was widely viewed as more trustworthy than clinton by a 59% to 36% margin, according to a CNN/ORC poll.

But it's unclear whether it's enough to doom her chances in November.

"Political science models all suggest that she will win in November unless there is a huge economic downturn of some kind," said Diana Mutz, a political science professor at the University of Pennsylvania who studies public opinion and its impact on mass political activity. "It’s the state of the economy, more than these kinds of things, that really matter in how people vote in November. Regardless of what did or did not happen, people tend to see this as partisan-motivated pushing and shoving."