Robert Mueller's report on Russian interference in the 2016 U.S. presidential election is 448 pages long, and when you're talking about a case this complex, things aren't always easy to figure out. However, we tried to get some basic answers for you.

Our expert is former federal prosecutor Paul Flannery, who now is a defense attorney for federal cases and founding partner of Flannery and Georgalis law firm.

1. Does the report exonerate President Trump?

Mueller's report says, "While this report does not conclude the president committed a crime, it also does not exonerate him."

"Investigations either result in charges based on the facts and evidence or they don't result in charges," Flannery said. "In these more what we would call 'white collar' type matters, there's often times more gray. It's not necessarily black and white."

2. Is it up to Attorney General Barr to decide if the president should be indicted?

Ultimately, the AG has concluded—after probably one of the most thorough investigations in the history of the criminal justice system—that there was insufficient evidence to conclude Trump committed a crime, although some have disputed his interpretation.

Flannery says proving an obstruction case beyond a reasonable doubt is one of the most challenging legal cases. Intent (usually covert) must be proven, and the president's public comments weren't evidence.

"It gives rise to inferences that the person didn't believe that what they were doing was wrong," he said. "Maybe mistaken, maybe not smart, certainly not smart politically, but was it criminal?"

3. Can a sitting president be indicted?

"Legal scholars would debate that as to whether or not it's possible that a sitting president could be indicted," Flannery said. "But the Department of Justice policy dating back to 1970 is that the Department of Justice would not support, would not support the charge of indicting a sitting president."

4. Is that why no charges were filed?

"The conclusion about whether or not there was sufficient evidence that the president committed a crime was based on the facts, not based on DOJ policy," Flanney said, adding the door has likely closed on Democrats using the Russia investigation for impeachment purposes.