The term torture refers to punishments which inflict severe pain or mutilation on prisoners. Governments, armies and tyrants have inflicted torture on opponents throughout recorded history, chiefly against slaves and rebels, but also against political or religious dissidents.
It is a matter of dispute whether it serves any valid purpose to distinguish between degrees or levels of torture. To some opponents, "torture is torture" and should always be prohibited.
In the West, the best known cases of torture were inflicted by ecclesiastical and political authorities during the Middle Ages. A well-known example from historical fiction occurs in Ivanhoe, and well-known examples from real history can be found in the Malleus Maleficarum, a manual for Witch Hunters.
The UN Convention against Torture and Other Cruel, Inhuman or Degrading Treatment defines torture as:
"...any act by which severe pain or suffering, whether physical or mental, is intentionally inflicted on a person for such purposes as obtaining from him or a third person information or a confession, punishing him for an act he or a third person has committed or is suspected of having committed, or intimidating or coercing him or a third person, or for any reason based on discrimination of any kind, when such pain or suffering is inflicted by or at the instigation of or with the consent or acquiescence of a public official or other person acting in an official capacity. It does not include pain or suffering arising only from, inherent in or incidental to lawful sanctions." 
Torture is widely practised in many countries throughout the world as a means of intimidating the ruling regime's opponents. Since 1997, incidences of torture or ill treatment by the police have been reported in over 140 different countries, according to Amnesty International in Asia & the Pacific.  By far most commonly reported method of torture is physical beatings - other commonly reported methods include: 
- Rape and sexual abuse in custody
- Mock execution or threat of death
- Prolonged solitary confinement
- Electric shocks
- Suspension of the body
The US maintains that its coercive interrogation techniques are not "torture". Despite this, President George W. Bush used one of his first ever vetoes on the McCain Amendment, which was intended to prohibit torture in stronger language that was previously used.
Toture, and 'Degrading treatment' are prohibited by the Geneva Convention, which the Bush Administration insists does not apply to Enemy Combatants, the new category they created specifically to describe captives suspected of being Terrorists.
-  The Malleus Maleficarum
- Mind the Gap: Purpose, Pain, and the Difference between Torture and Inhuman Treatment by Christian M. De Vos