In general: The Inquisition was a church – civic institution for the research and eradication of heretical perversion. It was divided into the Roman or papal and Spanish inquisitions. The Inquisition was established by Pope Gregory IX in the first half of the 13th century, when it began sending inquisitors, judges who worked with the head bishop in every diocese. Two church orders were given the right to be inquisitors and root out the source of heretical malice. Those two orders being the Dominicans and Franciscans.
The primary aim of the Inquisition was the eradication of religious and political papal adversaries. Such adversaries as Jan Hus, Thomas Cranmer and Giordano Bruno. Those that turned rogue, Franciscans, Paulicians, Albigensians and Waldensians – religious groups declared heretics. Ultimately, they could have been even the most powerful order of knights such as the Templars, who fought for the liberation of the holy city of Jerusalem and the tomb of Christ. The Templars were terminated in 1314 AD upon the initiative of King Philip IV the Fair of France.
To follow: The Inquisition, trial and punishment of the accused and Torquemada