The New York Times reports:
Rudolph W. Giuliani said on Monday that he provided President Trump with detailed information this year about how the United States ambassador to Ukraine was, in Mr. Giuliani’s view, impeding investigations that could benefit Mr. Trump, setting in motion the ambassador’s recall from her post.
In an interview, Mr. Giuliani, the president’s personal lawyer, described how he passed along to Mr. Trump “a couple of times” accounts about how the ambassador, Marie L. Yovanovitch, had frustrated efforts that could be politically helpful to Mr. Trump.
They included investigations involving former Vice President Joseph R. Biden Jr. and Ukrainians who disseminated documents that damaged Mr. Trump’s 2016 campaign.
If you’re foggy on the details of the convoluted Giuliani/Ukraine story, the piece linked above will be quite helpful.