Halal means permitted, allowed, lawful or legal. In relation to food or drink it means that the food or drink is lawful, permitted or allowed for Muslims. Most food and drinks are considered Halal unless they are stated clearly in the Quran (Holy book of Islam) and Hadith (Prophetic sayings) as forbidden or non-Halaal.

It means prohibited, not allowed, unlawful, illegal. It is opposite of Halal.
Examples of Haram include the meat of dead animals and birds, flesh of swine, intoxicating drugs and alcoholic beverages.

Any food or drink which one cannot determine  if it is Halal or Haram due to insufficient information, unreliable evidence etc. is categorised as Mashbooh. One example of a Mashbooh product is Whey powder. Rennet is used in the manufacture of Whey Powder. Rennet can be derived from animal rennet as well as non-animal rennet. If it is derived from pigs or animals that are not slaughtered in accordance with the Islamic law them it will be Haram. If the source of rennet is not known then it will be classified as Mashbooh. According to the following Hadith, Muslims must not consume anything which is Mashbooh.

 “Halal (Lawful) is clear and Haram (unlawful) is clear; in between the two are doubtful things, which people may not know whether they are Halal or Haram. One who avoids them in order to safeguard his religion and his honour is safe. Anyone who gets involved in these doubtful things may fall into the Haram (unlawful). This is similar to one who grazes his animals near a Hima*; it is quite likely that his animals will stray into it. Indeed, every King has a Hima and Hima for Allah is what He has prohibited”    (Al-Bukhari, Muslim)

*Hima - the grounds reserved for animals belonging to the King which are prohibited for other animals