The dossier is at the center of a legal and political mess with near-constant new developments. Here's a very basic summary,
with help from the Washington Post: The American company Fusion GPS started doing research on several Republican candidates during the 2016 campaign at the direction of the
Washington Free Beacon. A lawyer for the Hillary Clinton campaign and Democratic National Committee retained Fusion GPS from April 2016 to October 2016. Fusion GPS then hired Christopher Steele, a former British intelligence officer, who eventually compiled the dossier—of which Clinton staffers say they weren't aware.
BuzzFeed
published it in January 2017. The Justice Department appointed Robert Mueller to investigate Russia's meddling in the election in May 2017. Mueller's team then met with Steele as part of the probe,
according to the Associated Press.
Somewhere along the way, one of the claims in the dossier—that Trump paid prostitutes to urinate on a Moscow hotel bed where Barack and Michelle Obama had once slept—went viral. The "golden shower" dossier got its nickname and, given the rumor that the Kremlin has video of the incident, has sparked many "pee tape" jokes.