The word halal comes from Arabic and can be translated as "permitted or pure". Foodstuffs that comply with Islamic regulations are summarized under the term halal. On the other hand, foods that do not comply with Islamic regulations are summarized under the term haram. The food regulations are regulated in the Koran, the holy book of Islam, and in the Sunna, which contains the life, teachings and deeds of the Prophet Mohammed. In general, all foods are permitted except those that have been expressly or clearly forbidden.
The Koran clearly states which foods are forbidden for Muslims, i.e. Haram:
" Prohibited to you are dead animals, blood, the flesh of swine, and that which has been dedicated to other than Allāh, and [those animals] killed by strangling or by a violent blow or by a head-long fall or by the goring of horns, and those from which a wild animal has eaten, except what you [are able to] slaughter [before its death], and those which are sacrificed on stone altars, and [prohibited is] that you seek decision through divining arrows." (Sura 5, Verse 3)
It is widely known that the consumption of pork and alcohol is not permitted for Muslims. However, the Koran lists other foods that are not permitted.
O you who have believed, eat from the good things which We have provided for you and be grateful to Allah if it is [indeed] Him that you worship. He has only forbidden to you dead animals, blood, the flesh of swine, and that which has been dedicated to other than Allah. But whoever is forced [by necessity], neither desiring [it] nor transgressing [its limit], there is no sin upon him. Indeed, Allah is Forgiving and Merciful.
They ask you, [O Muhammad], what has been made lawful for them. Say, "Lawful for you are [all] good foods and [game caught by] what you have trained of hunting animals which you train as Allah has taught you. So eat of what they catch for you, and mention the name of Allah upon it, and fear Allah." Indeed, Allah is swift in account.