Halal is an Arabic term meaning permissible or lawful. The opposite of Halal is haram, prohibited or unlawful. Traditionally, Halal refers to food and beverages that are permissible for consumption by Muslims.
Broadly speaking, all foods are generally permissible except for those derived from prohibited animals, as well as food and beverages containing alcohol and other harmful or poisonous ingredients. Animal slaughter must be carried out in a humane and Shariah-compliant manner, with the intention that it is performed in the name of God.
Any food or drink which lies within the grey area and does not fall clearly under the Halal or non-Halal category is classified as Syubhah, alternatively called questionable or dubious. In this category, until the status becomes clear, Muslims should avoid consuming Syubhah food or drinks. The Prophet (peace be upon Him) has given a guideline concerning Syubhah matters. It is reported by Bukhari, Muslim, Abu Daud, Ibn Majah and Darimi, as follow:
الحلال بين والحرام بين وبينهما مشبهات لا يعلمها كثير من الناس فمن اتقى المشبهات استبرأ لدينه وعرضه ومن وقع في الشبهات وقع في الحرام
What is Halal is clear and what is Haram is also clear. However, in between those two is a dubious area which many people do not know about. He who distances himself from it has acquitted himself (from blame) and he who falls into it, has fallen into a state of haram.
Besides fulfilling the Shariah law, which is a must for Muslims, the food safety factor is a significant contributor in determining the toyibban i.e. wholesome (safe, clean, nutritious, quality) aspects of the food.