Alsalamu Alaykum
In Islamic jurisprudence, haram is used to refer to any act that is forbidden by Allah, and is one of five Islamic commandments (الأحكام الخمسة (al-ahkam al-khamsah)) that define the morality of human action. Something forbidden is what Islam has prohibited and has forbidden being done absolutely. Acts that are haram are typically prohibited in the religious texts of the Quran and the Sunnah.
The most remarkable reason to forbid something in Islam refers to its considerable harm, no matter is physical, mental, economical, social and so on. For example: gambling lead