Punishment is the inflicting of a penalty for a wrongdoing. Most often, this is in the context of a legal judgment - for instance, a legal penalty for a crime. Punishment often includes a moral component - the punishment is inflicted in order to show that such an act is condemned by the law, by society or those in charge. The justifications for punishment are often both retributive and consequentialist - for instance, that it reforms the characters of wrongdoers, makes them aware of their wrongdoings, makes the public aware of their status, makes amends to the victim, and also incapacitates the person.
Criminal penalties can include fines (including on-the-spot fines administered by Police officers, for example in the United Kingdom), imprisonment, community service, curfews and house arrest often using electronic tag-based monitoring, and restorative justice. Some societies use judicial corporal punishment (flogging, caning etc.) on convicted criminals. Some have used rather more violent and Biblical punishments - chopping the hands off thieves, for instance. Sex offenders in some areas are often required to undergo chemical castration (the State of California allows it as a punishment for those convicted of molesting children under the age of 13). Less widely practiced in contemporary societies, public humiliation (such as the stocks or pillory) has been an important part of the history of punishment - some judges in the United States still use a form of public humiliation by, for example, making an offender stand outside the store they stole from wearing a sign describing their crime.
Almost by definition, capital punishment - the death penalty - is the strongest punishment that can be imposed. This is used in many countries for serious crimes - in certain states of the United States, capital punishment can be given for particularly egregious murders (serial killings, murders of on-duty police officers, murder of children). Some countries impose the death penalty even wider - China uses the death penalty for a much wider range of offences. The death penalty certainly incapacitates an offender and prevents any further offences. Proponents of capital punishment also claim that it has a preventative role - you don't commit murder if you know that you could be executed for doing so. This is doubted by opponents of capital punishment, who point to the fact that most murders are crimes of passion, and are done in spite of the threat of punishment. Capital punishment is certainly retributive - opponents describe it as being driven by excessive and primal feelings of revenge and bloodlust.