A whistleblower complaint released Thursday details efforts by Trump and his attorney Rudy Giuliani to pressure Ukrainian officials to investigate former Vice President Joe Biden and his son Hunter. These are the main players in the complaint and the impeachment investigation.

Hunter Biden

Joe Biden’s son, who served on the board of directors of Burisma, an energy company in Ukraine

Joe Biden

Former vice president and Trump’s potential rival in the 2020 presidential race

Rudy Giuliani

Trump’s personal lawyer, who served as an intermediary between Trump and Ukraine

Nancy Pelosi

Speaker of the House who announced the impeachment inquiry last week

William Barr

U.S. attorney general who was mentioned in Trump’s phone call with Zelensky

Gordon Sondland

U.S. ambassador to the European Union, who met with Zelensky the day after the call

Kurt Volker

Former U.S. special representative for Ukraine who abruptly resigned his post on Friday

Andriy Yermak

A close aide to Zelensky who met with Giuliani in Madrid in early August

Marie Yovanovitch

Former U.S. ambassador to Ukraine since 2016 who was abruptly recalled in April

Volodymyr Zelensky

President of Ukraine who took office in May and is a former TV actor