In particular, this was about Trump having sex with a couple of different people, including one where his wife had recently given birth, and wanting to hush it up for the election. 

NYMAG

Michael Cohen said in district court on Tuesday that he had committed campaign-finance violations at the direction of President Trump, an enormously significant disclosure that could spell major legal trouble for the president.

Specifically, Cohen said that he had paid hush money to two women, Stormy Daniels and Karen McDougal, to buy their silence in the run-up to the 2016 election “in coordination and at the direction of a candidate for federal office” referred to as “Individual 1” in the government’s charges. These payments were made, according to the plea deal, “for the principal purpose of influencing the election.”

Michael Cohen's prosecutors granted immunity to David Pecker of the National Enquirer. 

In exchange for immunity, Pecker met with prosecutors and described details of the deals, which were arranged by Trump's former lawyer and fixer, Michael Cohen, the news organizations reported.

Pecker told prosecutors that Trump had knowledge of the deals, the Journal reported