In Article I of the Constitution, it says theHouseshall have the sole power of impeachment and the Senate shall have the sole power to try impeachments.
But the process has evolved over the years. The Constitution does not include the term "articles of impeachment," but a November 2019 Congressional Research Serviceanalysis of the impeachment processexplains what they are.
"The House impeaches an individual when a majority agrees to a House resolution containing explanations of the charges," according to the report. "The explanations in the resolution are referred to as 'articles of impeachment.'"
Once articles of impeachment are approved in the House, the Senate takes those allegations and conducts a trial considering whether to remove a President from office. The Constitution mandates that the chief justice of the Supreme Court presides.
A President may be impeached and removed for "Treason, Bribery, or other high Crimes and Misdemeanors," according to Article II of the Constitution. There's no hard and fast definition of those, so Congress has the ultimate say.
Democrats prepared two articles of impeachment against Trump, for abuse of power and obstruction of Congress.