The Wizengamot is the high court of wizarding law in Britain. The head of the Wizengamot is called the Chief Warlock. Dumbledore held that post for years, but was temporarily removed from the post during the summer of 1995 [Y15]. He was reinstated in June of 1996 [Y16]. Those who preside over a hearing or a trial are called the Interrogators. A Court Scribe takes notes of the proceedings. Wizengamot members wear plum-colored robes with an elaborate silver "W" on the left side. Other members of the Wizengamot include a dumpy wizard with a large black mustache and a frizzy-haired witch, both allied with Fudge against Dumbledore and Harry, and two elderly witches who were apparently friendly to Dumbledore.
The full Wizengamot sat in judgement of Harry Potter on August 12, 1995 [Y15]. The hearing took place in Courtroom Ten, which is located on Level 10 of the Ministry of Magic. This courtroom is identical to (and may very well be the same one as) that which Harry saw in the Pensieve when he "attended" several proceedings from Dumbledore's memory. The walls of Courtroom Ten are dark stone, dimly lit by torches.
In the center of the room is a chair with magical chains on it where the accused sits. The court members, of which there are about fifty, sit above overlooking the chair in the judge's balcony. When Harry was being accused, Amelia Bones herself presided. She sat to the left of Cornelius Fudge. Umbridge sat to Fudge's right.
According to the Wizengamot Charter of Rights, the accused is allowed to call witnesses in his or her defense and to be represented by another person. Harry was represented by Dumbledore, much to his surprise, and Mrs. Figg was called as a witness for the defense.
The Wizengamot gets its name from the Witan, also known as the Witenagemot,
from Anglo-Saxon England. Witan is defined as "an assembly of
higher ecclesiastics and important laymen, including king's thegns, that met
to counsel the king on matters such as judicial problems."