On Friday, House Republicans releaseda hotly disputed memo that they say shows unjustified surveillance of Trump officials in the FBI's investigation of their ties to Moscow.Adrian Morrow explains what the memo is about and what it doesn't say

It is a four-page memo that has pitted President Donald Trump and House Republicans against the FBI and the Department of Justice, transfixed the U.S. media for the better part of a week and taken up nearly all of official Washington's bandwidth.

The document, written by the staff of GOP House intelligence chairman Devin Nunes, is a summary of information provided by the Federal Bureau of Investigation and the Department of Justice about the process behind obtaining a surveillance warrant for a former adviser to Mr. Trump as part of an investigation into Russian meddling in the 2016 election. The memo did not point to any illegality, but to some in the GOP, it reveals scandalously slipshod work in obtaining the warrant – and an anti-Trump bias in the nation's top law-enforcement agency. To others, it's a partisan memo that uses cherry-picked information to unfairly smear the investigation. To the FBI and DOJ, which pleaded with Mr. Trump not to authorize the memo's release, it dangerously exposes investigative techniques and sources.

So what's actually in the memo, which was released midday Friday after weeks of wrangling? Here are six key takeaways.

A who's who

1. The central thrust of the document is that the FBI and Department of Justice used a dossier compiled by a former British spy to obtain a surveillance warrant for an adviser to Donald Trump's presidential campaign – without disclosing to the court that the ex-spy had been paid by Hillary Clinton's rival campaign. The dossier, which contains a series of claims about Mr. Trump and his circle's ties to Russia, was assembled by ex-MI6 agent Christopher Steele. He was commissioned by a Washington research firm named Fusion GPS, which had been hired by the Clinton campaign to dig up dirt on Mr. Trump. The memo says that the FBI and DOJ used the dossier as part of a successful application tosurveil Carter Page, an oil-industry consultant who advised the Trump campaign on foreign policy. Mr. Page, who has long had business ties to Russia, was suspected of being an agent of the Kremlin after having a series of contacts with Russian spies and government officials, and expressing views sympathetic to Vladimir Putin. The FBI obtained the warrant from the Foreign Intelligence Surveillance Act (FISA) court, whose proceedings are secret, in the fall of 2016. It was subsequently renewed by the court three times.

2. Mr. Steele regularly gave the information he was gathering to the media. One of these leaks, to Mother Jones magazine in October, 2016, led the FBI to "terminate" him as a source, the memo says. The Mother Jones piece in question, published a week before the election, refers to "a former senior intelligence officer for a Western country" who was passing information on Mr. Trump to the FBI.

3. The memo says Mr. Steele told a contact at the Department of Justice, Bruce Ohr, that he was "desperate" and "passionate" that Mr. Trump lose the election. Mr. Ohr's wife also worked for Fusion GPS doing research on Mr. Trump. The memo asserts that Mr. Steele's comments show ideological bias against Mr. Trump, and that both this and Mr. Ohr's family connection to Fusion should have been disclosed to the FISA court.

4. The GOP says Mr.Steele's dossier was "only minimally corroborated" by the FBI's own investigation but that then-deputy director AndrewMcCabe told the committee the bureau would not have sought the warrant without it.

5. Somewhat in passing, the memo confirms that the FBI investigation into Russian election meddling actually began nearly three months before the surveillance warrant on Mr. Page. In its final paragraph, the document says FBI agent PeterStrzok launched the probe in late July, 2016 because of information about GeorgePapadopoulos, another Trump campaign foreign-policy adviser. Mr.Papadopoulos, who would end up pleading guilty to lying to the FBI, tried to set up a meeting between Mr. Trump and Mr. Putin, and learned that the Russians had copies of embarrassing Democratic e-mails before they appeared onWikileaks. Mr.Strzok, for his part, was later removed from the investigation when special counsel Robert Mueller learned he had disparaged Mr. Trump in text messages to FBI lawyer Lisa Page, with whom he was having an affair.

6. There are some obvious gaps in the memo. For one, it doesn't say what other information the FBI presented to the FISA court to get the warrant: Did the Steele dossier represent 90 per cent of the FISA application, 50 per cent or 1 per cent? The memo doesn't tell us. Mr. Page had been on the government's radar since at least 2013, when he met with two Russia spies, which suggests the FBI had reasons predating the Steele dossier to target him. And the memo itself makes clear that the investigation had already begun months before the FISA warrant, but does not say if the FBI dug up information in the probe that was then used for the warrant. It's also unclear from the memo whether the FBI corroborated any of the dossier's claims; one paragraph says the corroboration was "minimal," but this leaves open the possibility that agents did, in fact, verify at least some of what Mr. Steele reported. It also doesn't mention that Fusion GPS was originally paid by Republican opponents of Mr. Trump, focusing instead purely on the Democratic connection.

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