The Mueller Report Will Be Released on Thursday. Here’s a Guide.

WASHINGTON — After 23 months, 500 search warrants, 2,300 subpoenas and a string of indictments, the results of the investigation by the special counsel, Robert S. Mueller III, will be public on Thursday in a nearly 400-page report. The treatise is likely to add significantly to our understanding of Russia’s 2016 election interference and President Trump’s efforts to control federal inquiries into the matter.

Attorney General William P. Barr said last month that the special counsel did not find that anyone associated with the Trump campaign worked with the Russian government to illegally influence the election. He also said there was insufficient evidence that Mr. Trump illegally obstructed justice. But Americans have been eagerly waiting to hear from Mr. Mueller’s investigators in their own words.

Whether you have followed every step of the investigation or are tuning in after months of avoiding the headlines, here is a primer for the report’s release.

Thursday morning, according to the Justice Department.

The Justice Department is expected to publish it on the special counsel’s website. The New York Times will be offering live updates and analysis of the key findings, as will most likely every major news organization.

Mr. Barr has said that law enforcement officials are blacking out sensitive information and that the redactions will be color-coded so we will know the reason behind each one. They will fall into four categories:

1. Information that has been presented to a grand jury, which is subject to secrecy rules. This could conceivably cover a lot of material.

2. Material that intelligence officials fear could compromise sensitive sources and methods. This would include information from F.B.I. informants and foreign allies.

3. Information that could hamper other current investigations, including spinoffs of the Mueller inquiry. Federal prosecutors in Brooklyn and Manhattan are investigating the finances of the Trump inaugural committee and hush payments intended to cover up a sex scandal that threatened to upend Mr. Trump’s campaign.

4. Material that the Justice Department believes would unfairly infringe on the privacy and damage the reputations of “peripheral third parties.”

Mr. Barr’s concerns are standard for prosecutors handling sensitive information. “It is not like that there is anything crazy on his list,” said Mary McCord, who led the Justice Department’s national security division from 2016 to 2017.

Prosecutors are prohibited under a federal rule of criminal procedure from disclosing grand jury material. They also try not to jeopardize intelligence sources and methods that contribute to the nation’s security.

They want to keep current criminal inquiries as quiet as possible to maximize investigators’ leverage and to protect the reputations of people who may never be charged with a crime. And they try not to publicly identify witnesses or other peripheral figures for the same reason.

“These are well-established principles,” Ms. McCord said. “But it remains to be seen how broadly or narrowly Barr applies them. And of course because we don’t know what has been redacted, we can’t make much of a judgment about whether he has been too broad or not.”

The only yardstick for the general public — a highly imperfect one — will be the percentage of the report that is hidden from view. “If nine-tenths of the report is blacked out, I think we confidently can then say, ‘Yes, that is too broad,’” Ms. McCord said.

Reporters are likely to make a beeline to the section of the report that addresses why Mr. Mueller decided not to draw a conclusion about whether Mr. Trump obstructed justice, citing “difficult issues” of law and fact.

Mr. Barr resolved those issues, deciding that there was insufficient evidence that the president had committed a crime. The report should either bolster that finding or call it into question.

Mr. Barr’s brief summation of the report’s main findings, released last month, suggested that prosecutors were unable to show that the president acted with “corrupt intent” to block the federal inquiry. The report is expected to address whether and why that was so. It may render some judgment on the president’s refusal to be interviewed in person and whether that hampered prosecutors.

Reporters will also zero in on what about the president’s conduct raised the possibility he may have obstructed justice. Mr. Barr told Congress last month that “a number of actions by the president” prompted concerns, “most of which have been the subject of public reporting.”

Mr. Barr’s comment implied there were troubling actions that have not yet been revealed. Does the report detail them?

We don’t know. The House Judiciary Committee has authorized a subpoena for the entire text of the report and the underlying evidence. The committee has not set a date to issue the subpoena. And Mr. Barr has said he is willing to consider whether he can share more information with the House and Senate Judiciary committees than he decided to release publicly.

But Democrats on the House Judiciary Committee are unlikely to be satisfied with a briefing or partial release; it appears likely that Representative Jerrold Nadler, Democrat of New York and the head of the committee, will issue the subpoena.

Whether the committee would release whatever information it gets is unclear. The Justice Department would probably resist the public disclosure of information it has deemed confidential or classified, setting up a battle in court.

Far from it. Even if much of the nation has moved on to “Game of Thrones,” this saga will continue.

Mr. Barr pledged to investigate the origins of the F.B.I.’s counterintelligence investigation into Russia’s election interference, which Mr. Mueller took over in May 2017. Congressional Democrats want to scrutinize the decisions by the special counsel and the attorney general, as well as Mr. Trump’s own behavior.

Mr. Barr has voluntarily agreed to explain his decisions to the House and Senate Judiciary committees in early May. The House committee is also likely to call Mr. Mueller to testify.

House Democrats are busy with their own investigations into matters related to the Mueller inquiry, including whether the president abused his powers or obstructed justice and whether foreign governments exerted improper influence over Mr. Trump and his family.

In the Senate, the intelligence committee is still working on its own report that will address some of the same questions that the Mueller team investigated. Lawmakers may propose policy changes to protect American elections from future foreign interference.

In short, the cottage industry of investigators that has sprung up in the past two years expects to be busy until at least the next presidential election.