A more thorough explanation:

Cruel and unusual punishment is a phrase used in the Eighth Amendment of the U.S. Constitution. This amendment prohibits cruel and unusual punishment. However, the Constitution does not give more guidance than that, and so courts have heard a number of cases which have given guidance to the prohibition on cruel and unusual punishment.

• Imprisonment: A sentence may not be disproportionate to the crime committed, regardless of whether the crime is a felony or a misdemeanor. For example, a life sentence without parole for a juvenile non-homicide offender is unconstitutional.
• Prison Beatings: The unnecessary and wanton infliction of pain constitutes cruel and unusual punishment. For example, handcuffing a prisoner to a hitching post for 7 hours, taunting, and denying bathroom breaks exceeds what is necessary to restore order.
• Conditions of Confinement: A prison guard's deliberate indifference to a prisoner's serious illness or injury would constitute cruel and unusual punishment which would violate the Eighth Amendment. Overcrowding in prisons that results in medical care violations is also considered unconstitutional.

These examples illustrate how the Eighth Amendment protects individuals from being subjected to punishments that are excessively harsh or inhumane. The Supreme Court has established guidelines to ensure that punishments are proportional to the crime committed and that prisoners are not subjected to unnecessary pain or suffering.