How would an impeachment inquiry against Donald Trump work?

Democrats are weighing impeachment after news reports suggested that President Donald Trump withheld U.S. military aid from Ukraine to pressure the country into investigating his political rival Joe Biden. Biden’s son Hunter was a director at a Ukrainian energy company when his father served as vice president. A complaint from an intelligence community whistleblower last month led to news reports that zeroed in on interactions between Trump and Ukrainian president Volodymyr Zelensky. During their call, Trump is alleged to have repeatedly pressed the Ukrainian government to investigate the Bidens after having ordered a hold on almost $400 million in U.S. ...