Democrats (namely Hillary, Obama, and the DNC) paid Russians (and agents of Russian businesses like Steele) to make up a disgusting story (called "the dossier") about candidate Trump which they then used to falsely swear out FISA warrants to wiretap Trump and his associates, family, and anyone who interacted with him, in a direct violation of the 4th Amendment, RICO statutes, and several federal laws against election interference.
...Basically the 4 page memo lays out exactly who broke what laws, how, and in what departments, and is a summary of a 99 page memo which supplies even more details about the crimes committed by the Democrats prior, during and after the election. It clearly proves that the FBI and DOJ (which are Obama holdovers) orchestrated and colluded to first try to ruin Trump's candidacy to ensure Hillary Clinton would be elected, then when that failed to further use the lies to try to destroy President Trump's administration after he was elected.
“A nation can survive its fools, and even the ambitious, but it cannot survive treason from within. An enemy at the gates is less formidable, for he is known and carries his banner openly. But the traitor moves amongst those within the gate freely, his sly whispers rustling through all the alleys, heard in the very halls of government itself. For the traitor appears not a traitor; he speaks in accents familiar to his victims, and he wears their face and their arguments, he appeals to the baseness that lies deep in the hearts of all men. He rots the soul of a nation, he works secretly and unknown in the night to undermine the pillars of the city, he infects the body politic so that it can no longer resist. A murderer is less to fear.”
-Marcus Tullius Cicero