Haram (həˈrɑːm,_hæˈrɑːm,hɑːˈrɑːm,-ˈræm; حَرَام, ALA, ħaˈraːm) is an Arabic term meaning 'forbidden'. This may refer to either something sacred to which access is not allowed to the people who are not in a state of purity or who are not initiated into the sacred knowledge; or, in direct contrast, to an evil and thus "sinful action that is forbidden to be done". The term also denotes something "set aside", thus being the Arabic equivalent of the Hebrew concept ḥērem and the concept of sacer (cf. sacred) in Roman law and religion. In Islamic jurisprudence, haram is used to refer to any act that is forbidden by Allah and is one of the five Islamic commandments (al-ʾAḥkām al-Ḵamsa) that define the morality of human action.
Acts that are haram are typically prohibited in the religious texts of the Quran, and the sunnah category of haram is the highest status of prohibition. If something is considered haram, it remains prohibited no matter how good the intention is or how honorable the purpose is. Sins, good, and meritorious acts are placed on the mizan (weighing scales) on the Day of Judgement and are weighed according to the sincerity of the doer. Views of different madhhabs or legal schools of thought can vary significantly regarding what is or is not haram based on the scholarly interpretation of the core religious texts (Quran and hadith).
Actions that are haram result in harm one way or another and are therefore considered a sin if carried out by a Muslim.
They ask you about wine and gambling. Say, "In them is great harm and (yet, some) benefit for people. But their harm is greater than their benefit..."
By bringing up the word "benefit" as an opposite to "sin", verse 2:219 of the Quran clarifies that haram is that which is harmful, in opposition to that which brings benefit; therefore, sin is that which hurts others or oneself.
An Islamic principle related to haram is that if something is prohibited or forbidden, then anything that leads to it is also considered a haram act.